The risk of military intervention from the United States is pretty much zero. What would be the objective of such an intervention? There’s no influential “Israel” or “domestic Cuban community” lobbying/manipulating for intervention in Vietnam. And Vietnam is not in Trump’s backyard.
Instead, Vietnam, like for example the Philippines, has the seeds of conflict with China due to, among other things, China’s extensive territorial claims in the maritime areas off Vietnam’s coast.
Regarding tariffs, Vietnam could indeed face new problems with the US due to its massive trade surplus.