Maybe it's related to overhead (benefits, contract law, payroll, taxes, etc). Speaking from experience, all that stuff becomes more complicated when you're doing it cross-border.
Probably due to time zone
Contrary to what Americans think, timezones are not exclusively an American thing, every country has them, and crazily, the entire continent (because the US is actually part of America, they are not all of it) shares them.
Nobody said that. They probably keep it in the US, so most of their employees are working at the same time and u don't have someone working when the rest of your team is sleeping.
I think the parent's point is that Canada, Mexico, Central America and parts of South America all have time zones close to (or identical to) PDT. So there are large populations that are no more than three hours away from PDT.
Ah, that makes more sense. Wonder if they'd make an exception.