Vietnam:  Nope, Kennedy could've pulled out.  Truman started our involvement.  Actually, it was us playing buddies with the French.  A big part of our struggles in the middle east is because of the colonizing French and Britains.  Now, we've taken over.  LOL

In later wars, the picture gets more fuzzy. 9/11 and Afghanistan?  Well, you could say we brought that on by Desert Storm. Or, you could say we brought that on by Reagan and arming the "rebels".  Or, you could go back to Jimmy Carter, when we first started arming those rebels, but much of the support came under Reagan.

Iraq?  Obviously we didn't HAVE to go in.  But, if you want to buy that global threat bull, you could go back to Hussein being heavily pimped by Reagan.  'Course you would have to go back to 1960 when we helped overthrow Iraq's government by supporting what was Hussein's party.

It's convoluted.  One things for sure...Dem or Repub, we meddle and love killing for personal gain.