A hostile takeover via war I sorely doubt in the immediate future. We're all getting more and more dependent on each other as countries. It'd spiral into a second great depression easily.
Now what I do suspect is a hostile takeover by debt. Would it really be so out of line for China to go "you owe us so much money, we'd forgive a lot of it if you give us...Alaska and Hawaii. You're not using them for much."