So your plan is... to cede Ukraine to Russia, cede Taiwan to China, and let the Kurds get slaughtered and have Iran build a nuke?
Sure, its annoying that there's problems all around the world, but we all know that no one else is going to step up to do something about it. If no one else is stepping up, then we should. That's about it.
Letting Iran's nuclear program complete would seem like a major mistake. Letting North Korea's nuclear program progress + their space / ICBM program progress is also a mistake IMO. Etc. etc.