In Vietnam, we didn't annihilate any country's military (arguably, the Viet Cong was largely crushed, but they weren't a national military; the NVA, which was a national military, wasn't crushed.)

So, even with the newly stated point, citing Vietnam as evidence of our ability to annihilate a country's military isn't really a good idea.

So without these occurrences, you're positing that countries like China and Kyrgyzstan (seriously?) would some how lose track of the fact that we spend more on our military than the entire GDP of most other countries, have shiny military tech coming out our ears, and have enough nuclear capability to make irradiated glass the only commodity left for them to barter with in their new found post-apocalyptic hell scape?

Bullies gonna bully, though.