Does Apple TV 4K support Apple prime Canada?

No, the App is one and the same. There is no such thing as an Amazon Prime app. The App is named Amazon Prime Video everywhere:

US: ‎Amazon Prime Video on the US App Store

The content is based on your region yes, but the app is the same app everywhere.

If you go to the U.S and access your Prime video app there, you will get the American content.

It supports the Amazon Prime app regardless of region.

Wether Amazon then supports 4K media through their app on Apple TV is a question for Amazon.  However, after a bit of research it seems they do, but you need to find the 4K content in a special way.

See here: How do I stream Amazon Video in 4K on App… - Apple Community

The "Amazon Prime" app I mentioned is the Prime Video app and is the same in all countries Amazon supports.

There is no other app to view Amazon Prime Video content.

Amazon Prime has more content than PrimeVideo

Amazon Prime app does not exist unless you're in an amazon country.

Outside Amazon countries you have primevideo app instead.

That said it would be rather negligent of Amazon not to have an Amazon app for Canada.

Amd if it does I expect it to work well.