We will use 2,500 of those pointy tipped packages on the middle east and another 2,500 in Russia and then we will have 200 million soldiers from China marching all over us. So essentially at some point we will lose. The next question you have to ask yourself is when.
You can’t transport 200 million soldiers from China across the Pacific to the US. The US’s geography will prevent invasion by all countries save one (that’s already going on — and it’s not such a bad thing actually…)
If you’re looking for a model of the collapse of US power, the Soviet Union in the 90s is a pretty good one. Another one would be the British Empire at the end of the 19th century.
Our friends in the mideast might convince us to join a new war with Iran but that will only hasten the collapse.