Star Wars is often "Schrödinger's Political Allegory" - the Empire is British/Roman/German but also American (if Endor = Vietnam, and Jedha = the Middle East), but the Rebels are somehow American too. Whatever side you're on, you can use Star Wars to cast yourself as the good guy, and the other side as the baddies.
I realise that Lucas has said that the ewoks in Return of the Jedi were representations of the North Vietnamese. If you look at Rogue One, though, Saw's men are called terrorists, they use IEDs, it's a desert environment ... so the Rebels are, um, ISIS? Who do we want to win again?
Star Wars has always been too flakey to say Rebels are definitely this, or the the Empire are definitely that. It's popularity, and it's use by people on any part of the political spectrum as a a recruitment tool, depends on the fact that the US is magically both.
Yoda was blind to the rise of fascism and got overrun by the emperor. He also supported a questionable system that clearly had lots of issues for hundreds of years.
Star Wars isn't an allegory to the Vietnam War. That's just something Lucas said to sound smart. At no point during the plot of the OG trilogy does it draw parallels to any of the real world events in the Vietnam War.
While interviewing Lucas on AMC in 2018, James Cameron said, "The good guys are the rebels. They're using asymmetric warfare against a highly organized empire. I think we call those guys 'terrorists' today. We call them 'mujahideen.' We call them Al-Qaeda."
Lucas agreed with Cameron, adding, "When I did it, they were Viet Cong." He explained that the Vietnam allegory was front and center in his mind when making the original "Star Wars" in the mid-1970s, as was the American Revolution.