Breathing too hard would also end the oxygen supply eventually, but trying to make any one factor the cause for the end seems to be a waste. You might as well b

Breathing too hard would also end the oxygen supply eventually, but trying to make any one factor the cause for the end seems to be a waste. You might as well be trying to find which one reason is responsible for the collapse of Rome. Or maybe you find that one thing about the USA that makes it intolerable in your opinion, but it will always pale to the multicausal.