Do big tech companies require on site interviews?
Every company will have its own procedures and likely other procedures that represent exceptions to the normal procedures. If a company is interested in you they will probably be able to find a way to make an interview happen. There are a lot of possibilities. Online interviews, via Skype and such, are becoming common at the early stages, at least, if not for final acceptance. Meeting a member of staff at a professional meeting in the US is a possibility. 

If they show interest and want an interview discuss your travel restrictions. The problems with US visas and such are well known, especially, I think, in Canada. If they are interested enough then they will probably suggest something. 

But at some point in the hiring process, companies like to have you visit your potential work site to meet a lot of people you'd be working with so you can get a sense about one another. They also like to show off the great work environment, especially if they really want you to join. That might be harder to arrange.