Invasion is always possible with a world population this size and a limited amount of farm land, oil, and sexually frustrated east indian/ chinese men.
America has some deep divisions right now tho, so i expect it will go into a form of civil war with martial law etc. Canada as well.
As far as limited strikes go, I haven’t much faith in humanity, its really hard to say what might happen. On one hand we do good things, on another we feed children to hungry dogs.
Its crop failure due to nuclear winter that scares me with the limited exchange. That and any kind of power plant problems due to emp… fukushima is a great example of a big problem that could kill everything in the northern hemisphere… (celebrate being alive, they fixed it finally as of the other week).
Never be afraid to do the righteous thing, nothing righteous is ever easy.