Thanks a lot for the answer @hechelion!
I've read up a lot more on this in the meantime, and at first it seemed like opening up an LLC as a foreigner would be the best idea because you technically shouldn't be taxed on work that you do outside the US. But it seems the law has changed recently and if income from places such as Itch counts as Royalty, you still have to pay 26% tax on it.
Oh well. I'll have to see if there's a different way for me to avoid double-taxation I guess. As per your example, with a sale in the US I'd be instantly 45% down, plus the 20% fees and taxes on my end, and I'd only take 35 cents on the dollar. And I'm pretty sure I'd face the same 30% withholding fee if I did the direct payment method too.
Thanks again though!