what I mean is the Lakota Sioux (and allied tribes) wouldn’t have necessarily considered themselves part the Unites States of America

Hence the war, sure. But then it ended badly, and now here we are.

I could point to a bunch of other failed struggles, from the Whiskey Rebellion to Blair Mountain to the Greensboro Massacre and call them "defensive conflicts", too.

It seems a weird response to be like yeah the USA has experience in fighting a defensive war, because of that time when doing genocide to First Nations they lost as the attackers.

I'm not sure what to tell you other than that the US is conquered territory. Residents struggle against the occupation regularly. And those struggles regularly fail.