I wouldn't rule out boots on the ground. In fact, if this war drags on, I'd say it's practically a certainty. That doesn't mean we'll see an American invasion, however. Much more likely is the use of CIA operators and military special operations for limited tactical incursions, and the use of U.S. Army Special Forces (Green Berets) as "advisors" to organize and direct the operations of local militias. We could also see the employment of international mercenaries like we have in Ukraine. I don't think the American public have an appetite to tolerate much more than that, barring some sort of 9/11-level false flag (and even that might backfire at this point).