"No reason."
The person you want to see elected President fought damned hard after he got back to make sure it was for "no reason."
I would give a lot to see you broach this thesis to some of the Vietnamese living around here.
If the American Left had gotten its way in every foreign policy issue in the past thirty years, half this planet would be a slave state, with the rest going fast. In every conflict America was involved in, political or otherwise, the leadership on the Left, eventually including the Democratic Party, took the opposition's side. This hasn't changed much.