Is this something we should do? I'm not convinced. Interfering in markets works only in the very rarest of circumstances. Fear of invoking the Law of Unintended Consequences should outweigh this rush toward solving any housing issue through politically expedient measures. Once again, sorry dawg, it's a no from me on this.
That said about the only way to slow foreign buyers is for reciprocal government reporting of any transfer of funds between US and Foreign banks greater than $10,000, and less than $2m - business or personal. Some behaviors will change - opening accounts in US based banks rather than local banks to skirt some of the reporting - for example. That'll stop them rooskie olegarkies from buying up all the best condo units in Boca.
A second method would be adding a 2% surcharge to all cash purchases - you know.... for affordable housing! That's something Gavin might fly up the flagpole since he's going to sell himself as a champion of low income housing. Yes, if Granny sells her igloo up in Saskatoon and wants to pay all cash for her condo in Palm Desert, it might cost an additional $2k to do so.
Neither of these things will ever happen. The NAR, Banks, AARP, and Homebuilders will turn their campaign contributions off should either of these be even whispered about. Remember, the only people politicians listen to have first names of either George, Abraham, Alexander, Ulysses, or Benjamin.
My .02c