> If what you say is true, why ever would the US want to defend them?

Ho Chi Minh went to the Americans and asked for help because the French were raping the Vietnamese and other things. The Americans refused to help them. So the Vietnamese asked the Communists for help. It is strongly believed that the American-Vietnamese war would have been adverted and Vietnam would have had a similar economic trajectory as Japan and South Korea after WWII if the Americans had helped.

Bill Clinton who learned from history did the opposite as Harry Truman and put two aircraft carrier strike groups between the island and the mainland during Taiwan's democratic election defending both democracy and Taiwan self determination.

There were a few American presidents who promoted and defended democracy. Unfortunately the whiny snowflake administration in power now isn't one of them.