Sorry, Hang.
Advance in another direction, because the overwhelming forces of History have you surrounded.
Truman started the MAAG with 35 guys but I haven't (as yet) found the max number under Truman before Ike took over. I suspect it could have been 342, which was a Geneva Accord limitation.
It is documented that under Ike, MAAG advisors were 342 in 1954. By 1961, MAAG's strength, had increased to 692 persons. I have been unable to document the progress of that increase, but it's clear that when Kennedy took over, this is about where the US troop strength was.
In any event, Kennedy is the guy who put Regular US troops into combat situations in VietNam. Absolutely incontrovertible fact. Under his direct authority, Regular US troops in VietNam went up to 16,000+. In combat.
Kennedy started it. Period.
What would have happened if he lived? Nobody knows. Would he have pulled out? Would he have escalated? His bright boy, McNamara, was ALWAYS for escalation. Kennedy seemed to listen to that dipsh*t in the same way that LBJ did. Cost a lot of US families their sons, that bastige.
You are right in that it wasn't a Dem/Repub thing. They all screwed the pooch. Indirect involvement did start with Truman, continued with Ike. (Remember the thread about Washinton's Farewell address? He was so RIGHT. Stay the fork out of other countries squabbles and internal affairs.)
Direct Combat Involvement of US Regulars started with Kennedy. Sorry, chum, you can't argue History. That's the way it was.
In his brief tenure, he screwed the Cuban Exiles ("just say NO"), totally sold out Diem (crook that Diem was, he didn't deserve what he got from Kennedy's administration) and sent US Regular troops into combat in VietNam. Not bad for 1000 days of "Camelot"... and these are only the ones we've discussed so far.