Russia and America are colonial powers, the Soviet Union most definitely wasn’t, but they claimed the land of the previous regime including all the bits that were stolen. Colonialism in Russia wasn’t as bad as it was in the United States but it was still colonialism. Why didn’t the Soviet Union turn Siberia into one or multiple soviets like they did East Germany or Ukraine? Why did Russia get to keep it?
As for the United States I don’t see indigenous and black people being happy about the United States existing even as communist state, Mexicos claims to the south west are arguably still valid, would a communist United States return it? There’s also the glaring issue of all the islands that have active independence movements, most notably Hawaii and Purto Rico, probably wouldn’t want to associate with a communist United States even if they were independent. Is the scars of slavery, colonialism, and genocide too much for a communist United States to bare? Was colonialism in Russia small enough that a communist state could claim lands that the previous regime stolen that any actual leftist power in the United States couldn’t?
I know ideally states shouldn’t exist but certainly the path forwards would require some kind of left wing American state(s)? How much of the colonial project of the United States can be claimed by revolutionaries, it can’t be as much as Russia?
This would depend on the conditions under which the current US territories would ever become socialist.
For example, American Balkanization could happen before any kind of adoption of socialism in its current territories. The dividing lines and timeline (how long since Balkanization) would determine whether those new borders were held up by any socialist project.
Also it's possible that the conditions under which socialism would have a chance in the US territories in any semi-near future (let's say 50 years because I can't imagine the current populace having revolutionary potential) would be a result of federalism + chuds constantly fucking us over to the point of unrecoverable crisis. In that case, it would be up to any revolutionary government to decide what to do with the remaining right wing remnants, and that would depend on the outcome of the inevitable civil war that led to said revolutionary government. Basically... what would they feel the need or desire to do to, say, the people who nuked three megacities? Who scorched the earth of your agricultural centers? Or maybe they didn't do that, so reeducation is in the table. Basically... it all depends on the actual material outcomes of the crises, the wars, the power base of any revolutionary government.