synchronize all my product listings across all North America Unified Account {USA, Canada and Mexico}

This is regarding a North America Unified Account

I have tried to synchronize all my product inventory with photos etc. from my USA Amazon handmade account onto Canada and Mexico with no success whatsoever. I have tried uploading an Excel file and used BIL {Build International Listings} to no avail.

Maybe I am downloading and uploading the wrong Excel file?

I keep getting error after errors.

Which files do I have to download and fill in to then upload to Amazon Canada market?

I read that BIL does not create the product listings but only keeps track of inventory. One would think it does integrate all the necessary features.

BTW I have a professional seller account and have connected all 3 marketplaces already.

This is very confusing and frustrating. Anybody who can guide me would be extremely helpful.