I know that foreign GMs who play in tournaments in the U.S. are extended “tournament courtesy” and do not have to be members of USCF to have the tournament rated. How far down does this courtesy extend? Are IMs and FMs eligible for it too? What about any foreign player with a FIDE affilation of a non-USA country?
The waiver of membership requirement applies to foreign GMs, IMs, WGMs, and WIMs. This is clearly covered in the FAQ page for the TD/Affiliate area (Part 2 - “Using TD/A”).