Mnementh on 05 October 2017
Well, first of all, Vietnam is as capitalist as it gets, communist my ass. Second of all, several members of my company were in Vietnam for business, it should be no biggie (we're german). Maybe they are not too happy about americans (remember, they had a war), but afterall it's all some time ago.
The biggest problem for you might be the army itself. I know in sensitive jobs (and military is included), people often get background checks. So I don't expect problems for you in Vietnam, but maybe from your superior officers. Dunno though how it is handled in your army.
Besides from that, check the climate at the time of your travel. At some times Vietnam is unbearable hot and rainy.
