there would be a power vacuum in several areas like Iraq and afghanistan, and civil war would break out. Also, countires would consider the US to be pussies and even more would ignore what the US says like Korth Korea and Iran. Likely we would see some contires make land grabs if they percieve a lack of US resolve. China taking Taiwan is possible, Russia taking Chechnia is more likely. African countires killing each other is almost certain. But then again they do that now anyways so thats not much of a change