I was going to say the world could just call up 500,000,000 people & bum rush us, though in reality most countries have far inferior mobilization capabilities. That aside, I don't know how much the United States could do without nukes before other countries could begin invading in large numbers.
Really, I don't know.
Also, it's not easy to get them all across that water
Another thing that occurred to me is that is the rest of the world acting as a host of separate entities or is it acting as a unified hive mind? That would be pretty important in how well we hold out.
