my guess it's about timezones and visa.
having 3 hours between a coworker and you is not that of a big deal but having 9hours time difference can be quite cumbersome.
Timezone doesn't make sense for Canada and South/Central America. Visa doesn't make much sense either, plenty of startups work with remote workers, no visa needed and for European people they can visit for 3 months with a business visa, nothing required for that, just a valid passport. Also, I have many south american friends who got a visa easily while working for successful startups.
