Simple, if America committed itself to peace, then a lot of industries and corporations would lose a lot of money. War is good business, and it will continue to be good business for a long time.
One of the biggest myths from both its admirers and opponents is that that America is "democratic". It isn't democratic. Its founders despised democracy. In fact, back when America was founded, you didn't just have to be 21 to vote, you had to be rich white landowner to vote. It is oligarchy that is as American as apple pie, racist cops & tomahawk missiles.