> if Iran is unhappy with their government, they can deal with it. It is not a US problem

If Tehran contented itself with oppressing its own, it probably wouldn't garner too much attention. The problem is its regional proxies constantly causing a mess. It lacks anyone willing to come to its aid right now in large part because of that foreign policy.

Small not, but the US hasn't declared war. That requires an act of congress, and congress has continued to neutered itself more and more for decades.