This is sort of wrong, though. lucas has said he drew inspiration from all the tiny country vs. giant empire fights - american revolution, vietnam, the winter war, Yi Sun-Sen's defeat of Japan, etc.
Vietnam was the most culturally prominent in the US, but beyond the superficialities (little force defeats big force) the stories don't really track at all. Like: there was no deathstar moment, there wasn't even a single decisive victory (the US just got sick of the meatgrinder and public pressure overcame the political will to continue). The US also wasn't defeated then replaced New Republic style, the NV weren't going it alone in their fight against the empire and nobody threw Kissinger off a cliff at the end (mores the fucking pity),
He drew ideas from a LOT when writing it; presenting it like it was inspired by a single event is pretty disingenuous.