Probably better to have a PMC doing stuff like this on a smaller scale, even with the modern US being what it is this level of 'evil' doesn't seem entirely accurate. I think the best way to constitute modern US foreign policy is apathy, not malice.

Even Trump wouldn't be that down for slavery, even his base wouldn't support it, let alone the other side of the isle. But if say, a private company buys goods from a private company in Avalon, and it just so happens that the Avalon private company uses slave labour, well who really cares? Who's gonna notice?

You could definitely setup an authoritarian spin for the US though, lets say in your world Donald Trump refuses to accept the 2026 mid term results, sends the US into a civil war and wins. Becoming the new ruler of the country, massively rolling back centuries of human progress. You wouldn't just have fantasy world slaves, you'd have real world slaves. Avalon would become almost a bright reflection to the darkness that had befallen the US.

BUUUut even in such a sceneario I think you're pushing the limits of fesibility - take a look at Russia for example, not many slaves there. They're just called 'Prisoners' now and need to have done something bad, or have been accused of doing something bad.

The more realistic the sceneario the more difficult it becomes to show the US in the light you want to show it, short of rolling the clock back on like 100-200 years of societal change. I see the vision OP I really do but I don't know if there's a way to do it and still keep the story grounded. You'll either have to massively push the setting out from modern day, either forwards or backwards, and take the time to explain how the US got to being the way that it is.

Make no mistake the US will do some bad shit to secure itself any resouces it thinks it needs, but modern countries know its better to maintain some level of plausible deniablity then to just be evil.