Your absolutely right! With just a bare minimum of coordination there could be a complete failure of the entire US National Electrical Grid. There are some recent studies and reports on this very scenario floating around the internet and from one of these I was able to download, it was the opinion of the writer that the real problem is the age of our electrical grid. Many components are not made anymore, and why every failure takes more money and time to repair as they have to make-fit many of these repairs with newer components into an outdated substation or similar. Theoretically, each "patch" put in place puts more stress on the remaining older components, he showed to be not so theoretical but very actual. Almost the entire eastern seaboard is outdated by a whopping 40 years. The only reason it's still functional is the components were all American made at a time when American Made really meant something and why the entire world coveted American made anything!
It's projected that if there were an all out attack on our power grid and it succeeded at least 60%, the entire country would be without power for roughly 3-5 years and it would be another 3-5 years before all major cities were back online with an unbelievable 12-14 years for the entire grid to have been replaced with all new components!
All the undocumented individuals coming into our country is the largest threat to our national security that our country has ever faced in it's entire history! A few half-hearted trained civilians with cell phones could easily knock out so many more sub-stations than we could ever repair in time, and that's just one key part of our nation's defenses. There are other targets of opportunity that could literally turn each state into it's own battleground and have no communications other than hand-held to try and coordinate a defense from a large force of hostile combatants who have had free reign for 2+ years to get all their plans perfected.
What's really chilling is the fact that this is not even taking into consideration that these combatants are not going to be acting alone. They will definitely have massive support from offshore naval and air-forces knowing this is their one shot at taking down the giant and so you can bank on them bringing everything they have to bare on every possible front and this is exactly the scenario that everyone has preached like religion forever that just no way could ever happen.
If I were an invading force and certain projects were of a nature that they had to be made sure they would go as planned as everything else relies on the initial failure to snowball more failures and secure the victory, I would do exactly as has already been done for my test run to get total destruction requirements, hostile entry times and responses and so much more from a single seemingly random and ill-conceived angry-lashing-out and so not bring any unnecessary attention to your true motives, etc.
Extremely scary stuff and with an administration that I do not trust at all because of just too many very bad decisions and rampant corruption, I can't help but think we the citizens are going to "have to" form security groups and set up very quickly patrol zones most likely to incur enemy actions in order to bring this out in the open fast enough. We need to bring conclusive "red-handed" proof from many unconnected points of very connected actions for it to be taken seriously and the not have the enemy within media spin it into nothing and put everyone back to sleep again!

Hey all, new here, but not new to this frustrating situation. I've another take on this and the possible reasons behind the three-monkey syndrome (see-hear-speak no evil). It is at first maybe hard to swallow, maybe you think I'm crazy, maybe I am, but all I know is it "is" the only way to achieve what was thought to be theoretically impossible.

So, first, please understand this is not to add to the hysteria, confusion, prejudice or any of the possible negative effects resultant from this very crazy situation. I am bringing this to everyone's attention I can as it is what it is and you'll clearly see that very shortly and why it could be very important.

America is for all intents and purposes a country pretty much immune to conventional assault or invasion due to it's very specific and highly unusual geographic and geological configuration and actual physical makeup. For summary's sake I'm going to forgo certain names and so on of landmarks as the names aren't important as much as their presence.

On the Eastern and Western coasts of our country there is limited landing area, but sufficient for landing parties on either side. That is the extent of the military possibilities, even in the face of heavy defenses, of any other country attacking ours. From this point forward everything becomes increasingly more difficult exponentially and is due in most part because of the very large mountain ranges that run most of the north/south lengths of each coast, making any such attempt to invade the center-mass of our country, where they majority of our military's might resides and almost every resource we need to be self-sufficient in defending ourselves.

Once landed on our shores and all personnel and armor and so on are deployed for transport to the battle front, thus ends their ability to proceed forward with any success. They would have met with substantially more advanced defenses that would have eliminated at least one-quarter of the enemy forces. They are landed and have taken some losses. They are now ready to begin the march forward and inland.

Next they have to make their way through heavily populated areas which are most of the available landing points and one or two more with much less population, but rapidly accessible to near-by stationed US military defenses. Should they be blessed and have lady luck herself with them and make it inland, and through the most heavily armed civilian population that boasts even more small and medium arms than many other country's military forces, again with an unbelievable amount of luck and misfortune on America's side, then your would begin the long and absolute 100% fatal journey up the side of a gigantic mountain range that is heavily defended 24/7 by simple military presence and having the proverbial high ground of all high grounds to simply exterminate the enemy forces like like so many fish in a barrel.

It is estimated to be impossible for any known military force to successfully gain enough of an upper hand to ever gain the high ground, and without such, everyone dies as the rear will be closing-up behind you requiring constant forward movement to avoid fighting on two fronts, even though the second would be much the same as having a high ground mentioned earlier, but this is drastically offset by the forward fighting required and so your virtually guaranteed certain failure and death. Your surrounded in effect!

The ability to supply the high ground forces literally indefinitely from the heart of our country enjoying the resources and personnel that is in excess of so many more than any landing force could ever hope to pull off. This scenario is almost identical on both the East and West coasts, with minor inconsequential differences. The theory and fact of the matter has been mathematically proven and history has not to date found a military force willing to give it a shot. Literally nobody is that stupid. So we enjoy what no other country anywhere on this planet enjoys, and that is true autonomy.

Some may be asking well, what about the North and South, Canada and Mexico? British Columbia is much the same situation as the entire West coast of America. That's the entry point from which a force might stand a chance, other wise if they go more north they've got the whole of the Alaskan US military and the Canadian forces to slow them a bit until our jets could attend and evaporate their entire force in seconds.

Mexico and the gulf are different but actually an even worse fate as we have our interests as far South as well, South America, and the closer you get to America the more defenses you will run into and with the Mexican Cartels manned and armed better than most small country's military forces and so much more savage and lawless. I can imagine it's not on anyone's battle plan to engage a Mexican Cartel just before engaging the actual enemy any time soon!

Because of this we have never been assaulted nor invaded, except internally by our ourselves!(IE:
American Civil War). This is the only way America could conceivably be invaded by an enemy force. They would need to be already present. Take into consideration that even 20% of those entering our country estimated at two million. That's an effective ground force of 400,000 infantry!!!

But, it gets worse, much worse. We are clueless they are here, right? So they have the liberty to move about and even become employed at practically anywhere they choose. This could already be happening and most of our key installations that are public entities, businesses could very easily be compromised and every single asset or resource we expect to be just a phone call away, are in fact never going to respond in the emergency that ensues. That would have a very, very disastrous and quit possibly a complete National Failure, meaning they would take over and all that would be left is to capture the Capital and execute all standing politicians and administration, and we all know how easy that is to do, thank you Donald Trump! America is no more!

Lets just say that they are decent with counterfeiting identification! I mean they are right here where they are all made, simple to have a few employees at wherever, too, right? So, now we have a direct failure of our military or at a minimum the support for said military, which is really the same thing, and it is unknown until the critical moment it's when it is needed and simply not available. Well, to us, anyway!!!

Another big problem for them is without being armed themselves, and attempting to acquire so many firearms is sure to red flag even the greediest of Mafia Bosses into paranoia for themselves, at least! Where do they get the means to arm themselves? As mentioned in the beginning, American's are the most heavily armed civilian population on the planet. (No this is not a plug for gun control. This should paint the portrait of why)

There are so many scenarios that could have these individuals securing firearms from Americans, the least of which is to simply rob a house while the owners are at work. I cringe every time I say this, but they have had TWO YEARS to get busy, and even if they were incompetent civilians the odds are such with American home-owned firearms that they would easily prevail with plenty. At this stage we can stop because it's going to be wholesale slaughter of the American population when the coordinated bell is rung and actual Armageddon is released upon the unsuspecting citizens and military in the heart of our country where NO INVADING FORCE IS CAPABLE OF REACHING!

Except in this scenario which could so very easily already be in progress. Even at 10% which is 200,000 armed and critically placed enemy combatants literally standing, sleeping and living right next to every one of us right now! With some basic math, at 20% that's 8,332 combatants per 48 continental states EACH! At 10% 4,166 per state! that's a formidable when you know they are coming. It's some very serious carnage in every state at most critical points and military infrastructure!

As has been sounded in so many a cluster-fudge in so many battles past where the same tactics were pretty much 'taught' to us with no mercy: "CHARLIE IS INSIDE THE WIRE!"