If LBJ hadn't got into the mess known as Vietnam,
Pulled out of, surely? The U.S was involved in Vietnam before LBJ became President.
All we had there were advisors. Yes, we were "involved", but there were no American combat troops in Vietnam.
There were thousands of "advisors" there before LBJ. President Kennedy had every intention of pulling them all out but he was assassinated. I heartily commend John Newman's book,
JFK And Vietnam. Might still be in print but if not, your library should have it.