I’m in the process with an international seller. Just closed today, 45 days after making my offer. Obviously, that included ROFR, returning closing docs, wiring funds, etc. I think the seller is in Canada. No issues. Actually, it all moved quite quickly.
I did ask the title company to provide me proof of the tax holdback, in case the IRS contacted me at a later date. Something like a letter for proof, etc.
Otherwise, no hidden fees or anything like that.
Bottom line, less likelihood of a buyback through ROFR, but potential for longer closing and an additional step the title company takes with the IRS (that you need to make sure you have proof of).