I'm a foreigner (yes, I know, sorry, sorry) who is a "US Person" and thus needs to (and, to be perfectly clear, is happy to, I'm sorry, I'm not-sorry, I'm sorry about being not-sorry?) pay US income tax. The IRS system is, by far, the worst I've ever had to deal with, and in this I'm comparing the US to countries like Rwanda, where, for some weird reason, I'm also required to pay taxes. Getting an ITIN (sort-of like…
The challenge with an ITIN is it blurs into immigration, visa status, whether you are violating visa terms, whether your ITIN - which you can get on a tourist visa - is an indication that you're trying to build a life here when you're just supposed to be a tourist, and so on. That doesn't even get into property ownership, or being a director or shareholder in a US corporation with an ITIN and various visa types.