Conventional wisdom would have it that the country where a vehicle is produced is not an export market, but the lead-in content explains the situation fairly well (from 1999-2010, one could only buy a Mercury in the United States or in the Middle East).  In other markets, the car was sold as a Ford.  I think it should probably be left alone as is, but if not, the best course to take would be to mention in the timeline when Canadian sale of it as a Mercury (and overall) ended.