All the countries working together couldn't destroy America.
It would be very easy for any country with 3 little nukes to do it.
A small terrorist group -- if it had the equipment -- could do it.
Nukes could help wipe out the large cities and military command and control centers. 40 million dead possibly. Most nukes have clean bomb status with rapid half-life for radiation.
Nukes lit off at 300k cause a massive emp over about 600 mile radius. 3 of them take out anything that has a wire in it over continental US.
This is not theoretical. It is well known by people who know the physics of it, and was tested by both Soviets and the US. Here is the US study on it:
https://www.empcommission.org/It's the loss of all electrical devices that kills people, not nuclear radiation (which when lit off at that alt, about zero of it reaches people). No electricity, no pumps, no motors, no machines that need a wire, or circuits, or a coil. So, no cars, trains, airplanes, ships, water service, waste treatment, refrigerators, tractors, furnaces, gas, transformers, control systems, radios, light bulbs, backup generators, solar cells, flashlights, phones.
You are reduced in travel to how far you can walk or ride a bike. Supermarkets out of supplies in 1-2 days. Then no more food is coming. No water is coming your way if you are in an area without natural water. No waste disposal. Any refrigerated medicine gone after a week. Even a farm isn't going to work unless you can water it with a hand pump and have horse-drawn equipment.
It is too big a logistics problem for any nation to solve before huge numbers of people die off.
To invade America?
Maybe not. Maybe just to destroy it.
Even if the plan was invasion, it wouldn't happen early or overtly. You would frame some other country or group for doing it, so that US subs don't nuke you. Then you can get a piece of what used to be America later because it would be mostly vacant, and you could come in "to help" with all the other places sending in huge numbers of people to help. Take as much time as you need.
Survivors will band together and fight any invasion force. Enough military, police, and militia members plus regular citizens with shotguns will make them costly beachheads. There will be occupied areas of course.
Overall in continental US, it would be 90% of the population dead, and everything ruined. Anyplace without surface water in walking distance (that's a lot of territory) would have no one left, unless they have half a year of water storage. Cities would be dead from starvation and roving gangs of CHUD's. Overall, America would be a wasteland of death, misery, and murder, with little starving enclaves living in the iron age. At the mercy of whatever group comes in with vehicles and tech that works.
Tell me how a terrorist group control 6 million square miles?
They wouldn't.
China . . . Europe . . .
Not needed at all. See above.
I'm an American. I know how to think like an adversary. Think what plans they have.
That way, I have a plan to stop them.
If you or I survived it, we would be the equivalent of an iron-age peasants on subsistence farming. We wouldn't be doing anything other than hoping anyone who shows up is there to help.
Fortunately, it would take only $20B to avoid this risk. Unfortunately, Americans are nearly totally oblivious to it, and so nothing is being done.
