I'm sorry, I heard Canada, especially British Columbia is the main supplier of basis of fentanyl. It has to do with Chinese cartels too, functioning in Canada.
Where did you hear this from? The US has always said it is Mexico. Once or twice (as far as I know) they also blamed China. But I can't recall anyone ever saying it's Canada who is the main supplier of fentanyl. Do you remember where you heard this from please? I can't recall hearing Canada is the main supplier.
According to the US Drug Enforcement Administration, Mexico is the main source of fentanyl entering the US, while Venezuela’s involvement in global trafficking networks is limited primarily to serving as a stopover for cocaine shipments from South America.