Yes, the US didn't ever have an explicit export ban. But the US government had passed the Defence Production Act, then went to the vaccine manufacturers and made priority contracts with them. What did you think would have happend if the vaccine manufacturers had say no, we'll supply the highest bidder from our US plants first?

The only other production locations were in Europe, so guess where the vaccine manufacturers thought Canada's doses would come from?

Please don't fall for the obvious obfuscation from the US government.