[pdonis]

> Veteran soldiers, local knowledge, sympathetic populace, terrain advantage.

And lots of aid from the USSR and China. Aid from two superpowers sure helps in fighting one superpower.

> None of America's aims could have been achieved there meaningfully.

It depends on what you think those aims were. The aim of preventing South Vietnam from being taken over by North Vietnam was achieved militarily; then the US Congress threw it away.

> Big guys lose to small guys all the time.

Big guys lose to small guys that are being helped out behind the scenes by other big guys all the time, yes. If the small guys have no help from other big guys, then no, the small guys pretty much just lose.