Our hands were pretty much restrained in the Vietnam War. Restrained with a capital R. The firepower used and level of aggression officially sanctioned were nowhere near World War 2 or even the Korean War. Tough shit.
And since we weren't using ALL of our military strength, the NVs managed to go all the way south. The population being sympathetic to the NVs didn't help either. What do I care? Thailand, Malaysia and Singapore resisted communism and look where they are now. If the Vietnamese wanted to suck communist cock so much, tough luck. We did what we had to do.
Durr durr, China isn't loaning us shit. If we want to play like a bunch anal kids here, we tolerated their dumping and undervaluing of the yuan LONG FUCKING ENOUGH. If we want to be even MORE anal, let's calculate the value of all that compared to this imaginary "2 billion USD loan" you've been babbling.
And yes, we're still the most powerful. Deal with it. The truth hurts, I know. But it's fact. We've got the technology, our people are living more comfortably than most people in other countries, our military is extremely well trained and developed. Hell, life is good State-side.