When will America flex it's muscles?

As the most powerful nation on earth, why don't we? Diplomacy doesn't work. The UN doesn't work. We have the economic and military power to do anything. For example, this whole trade deficit(debt) with China. Why the hell don't we simply cancel it? What is China going to do about it? Are they going to cut off relations with us? No, they can't. It's trade with us that keeps there economy going. And oil...Why don't we simply invade Venezuela? We could do it in a week. We could invade the entire middle east within a matter of months and decimate radical islam.