Even if Russia could reconstitute its army enough (after another year or so of struggling against a non-NATO country) to attempt an invasion of Latvia, yes, I would have to support sending US troops because that's what NATO is there for. And a big reason why Putin invaded Ukraine, i.e. their pursuit of NATO inclusion.
Russia invaded Ukraine under Obama. He didn't under Trump. He was always going to invade Ukraine again if/when Trump left Office. You can deny it all you want.
But believing he's going to invade Latvia is fear-mongering at this point. He doesn't have the ability. If he had taken Ukraine in a couple weeks like he predicted, sure, he might have tested NATO. But after the B word slapping he would have received by the full force of all those NATO countries surrounding him and would have surrendered.
And if you think he's so irrational, why do you think being defeated in Ukraine would make him stop?