> You seem to put "American forces" in a special bucket where,

I'm a vet. My default setting is to support American troops unless they're shown to be acting wrongly.

> even if the actions the US military are taking is wrong,

That's a bizarre little strawman. No. I can support the soldiers, sailors, and airmen while believing their leadership is wrong. By civilian analogy, I support the employees of HHS even if I think their boss is an idiot.

> the support and reputation of "American forces" should still be protected at all costs, and the people they're doing wrong things to don't get to have any support.

Your words, not mine. I don't feel that way. American leadership orders all kinds of jackassery. The people doing their jobs, presuming they're not committing war crimes (sorry if that was going to be your next gotcha), have my support. I've not heard any accusations that the POWs Fonda "visited", as though Hanoi Hilton was a zoo and they were wildlife on display, were legitimately war criminals. If they were, I would not support them. I for damn sure would not have supported the North Vietnamese government against our own solders, though. If our guys were in the wrong, it would be perfectly possible to prosecute both sets of people.

> Let's imagine an alternate universe

Let me stop you right there. We don't have to invent increasingly contrived scenarios to debate the core case: is it OK to provide aid and comfort to the enemy? It's not. It doesn't mean you have to automatically say your own military is flawless, either. But in the common case, I'm vastly more likely to support the general actions of the US military over those of the People's Army of Vietnam. I don't think that's an especially hot take.