I know America isn't the only one with a big military, but we do have the biggest. Russia would hand over Snowden if they thought we would respond with war. China's military is relatively new, badly trained and their country would have food shortages if we stopped selling food to them. Not to mention that they have no nuclear arms at their disposal, whereas we have many.
I'm not saying the US military is unstoppable, but I feel it would win a war versus any two countries. (Especially if we got our allies involved. I'm pretty sure Canada wants to keep the status quo on their borders.)
EDIT: I meant to quote in reply. This is to Atreju.
Aaaaahm China DOES have nukes.In the nuclear non proliferation America even aggrees they may have them.That the world speaks mostly ENGLISH is not thanks to America.That's not gunboat diplomacy at all, baby....