I suggest location(s) are comma-separated in parentheses with a special value "Anywhere" for any country in the world.
Timezones should also be allowed, in which case they should be in brackets []. The assumption with timezones is that any country in the timezone range is allowed.
eg:
"REMOTE (Anywhere)"
"REMOTE (US, Canada)"
"REMOTE [UTC-1 to UTC-3, ET, PT]"
I had to take out the INTERNS and VISA bit in order to make it fit, but those (especially INTERNS) didn't seem to be much used.