To be clear, I'm not making accusations about Vietnam, I was just thinking about it and found it a little strange.
I can think of some fairly plausible reasons, but just because those reasons are plausible doesn't mean they're actually correct, so I was wondering if anybody had a more concrete historical and materialist understanding of the situation.
No, that's just Western cope, especially Yank cope that thinks Vietnam would be friendly to a country that poisoned their population with Agent Orange. The CPC and CPV are super friendly with each.
None of this speaks of any open animosity Vietnam has with China:
https://en.vietnamplus.vn/vietnamese-chinese-officials-talk-territorial-border-issues/271101.vnp
https://en.vietnamplus.vn/vietnamese-chinese-border-guards-join-hands-in-building-border-of-peace-stability/274524.vnp
https://en.vietnamplus.vn/trade-cooperation-bright-spot-in-vietnamchina-relations/274675.vnp
yeah... look up the history of sino-vietnamese relations in the 70s and 80s
it's better now, it was real bad before
The Western cope is thinking Sino-Vietnamese relations is the same in the 2020s as it was during the 70s.
I don't think anybody thinks that, certainly not here?
The OP's question was "why does Vietnam have a relationship with the USA and the DPRK doesn't" and the history of tensions with China is the reason for the faster-than-expected renormalization of relations
The Sino-Soviet Split and its consequences have been a disaster for the human race