Well usually it's levied at the border for physical goods so the importing company (usually not the end consumer for consumer goods) eats the cost (or prices it in/passes it to the consumer).

You're right though, with digital goods it's ambiguous. If the company has a US entity is that the importer? That's the scenario that popped into my (somewhat tired) head. Probably because Canada has been trying to impose taxes on US tech companies with a similar argument.

If you buy a good online in a separate country, where is the transaction made?