We would be stupid to go back.
Let the Chinese and the Vietnamese fight it out.
And didn’t the Chinese get it in the teeth when they tried it last time?
The Cong kicked Chinese ass with US made equipment left behind. After the USA left, Vietnam had the 4th largest Army in the world. And one of the best equipped.
Actually, China occupied Vietnam for more than a thousand years, from 111 B.C. to 938 A.D.
Vietnamese have very long memories when it comes to China. Their communist brethren to the north are also their biggest nightmare.
Politically it would be impossible to bring a U.S. presence back to Vietnam. We Vietnam vets also have long memories.