America is far safer with strong global alliances then through isolationism. 

Aid to other countries is a a tiny sum of money. Foreign bases are largely funded by other countries governments. 

If we don't want to play in global politics anymore, that's fine. China and Russia will gladly take our spot. But then I have to wonder why we need such a large military from this point forward? The last time a foreign force set foot on the continental US was something like 150 years ago.