Winners normally do not get overly worked up about the vanquished.

Vietnam for the most part stopped the anti-America propaganda in the nineties. Sure, everyone learns about the American war in the history books, but they're also exposed to the huge amount of movies, tv shows and music from America. Vietnam also had a decade long border dispute with China which started with the war of 1979 (funny enough, this is rarely mentioned in school), so hatred of China is common. In recent years Vietnam and China have clashed multiple times on the issues of South China Sea (the Vietnamese call this the "East Sea"). The enemy of my enemy is my friend, that kind of thing.

Not only Americans. Vietnamese people view white, Western people very favorably, since they generally look up to those developed nations (and their citizens).

And yes, part of the reason is that the enemy of my enemy is my friend.

Maybe they don't have anti-US propaganda, like North Korea does.