You cannot seriously be saying that a foreign country would...

You cannot seriously be saying that a foreign country would invade australia?. They would need a massive deployment over thousands of kilometres of ocean to control a land mass as big as USA. There would be retaliation by us and our allies that would hit them hard as well. Why would you do that and destroy the country when you can simply buy it as you do today.? The only reason a country invades another is to obtain the land and it's resources. They don't want the people. So if it is resources only you want then just buy the damn things.