I agree that the US army won't be able to compete wtih that kind...

I agree that the US army won't be able to compete wtih that kind of man power, particularly because China's new army will be a technologically advanced one.
Personally I don't think that the US can stop Iran from selling oil in euros ... they'll stand alone in opposing it (obviously because Europe will be welcoming this move)... and the US need Europe's support in this situation.
This is a very dangerous conflict indeed. The Iranis have the US lock stock ... if the US place economic sanctions on Iran, Iran will stop selling oil and create economic turmoil for the US and everyone else... if the US bomb Iran then they risk starting a world war with China and Russia (two very powerful enemies).
Iran may not be a super power, but they have 2 friends who are!