2023.20 Nort America Maps don't have Canada

Maybe the full map hasn't uploaded. If you have BaseCamp have a look to see what is actually loaded. It's a while since I used a 2797, so also check you don't have to select Canada first in the address search. If JaVaWa's GMTK program will run on your mac you can also use that to check the map coverage

GMTK is not supported by the Mac OSes since Catalina.    

Can you tell me how to completely wipe the GPS, it's maps, and reinstall from scratch?   

It is OK to delete all the files on the GPS volumes and format them via my Mac then let Garmin redownload and reinstall?   I have not solved my Canada issue, and this is my last resort.

No, that will turn your Garmin into a brick. You could try a hard reset but note that doesn't delete maps. If the advice I've already given hasn't helped try calling Product Support, but their first suggestion will be a hard reset so try that first. 

Incidentally if you zoom into areas of the map in Canada do you see a detailed map or not? If not that will explain why address search is failing.

If there's no detail then Canada isn't there. Did you ever have access to Canada? From what I can work out All US is just the lower 49 States 

Yes.  I Used it last in 2018 it to visit the very same friend I was planning on visiting this year (he moved) and had to resort to an international data plan and my iPhone to get there and back.  

So, while it ma be another two years before I do this trip again, I’m still truing to fix this issue.  How can I remove the maps?   I probably don’t have access to Mexico, either.  I’d like to fix this because the GPS is otherwise still usable, but just in the US only.  

This is the opposite of what I should see on my GPS (ignore the top two entries. I don’t have those.). On my Nuvi, I only have the bottom one under myMaps ALL US.   There is no ALL Canada & Mexico entry to check. 
This is why my Nuvi doesn’t find any Canadian addresses.   They’re somehow not loaded.   Reinstalling the maps did not affect it.   That’s why I was hoping to try a wipe and reinstall.   
Garmin seems to hold the file information close to its chest as there is very little info online outside of following the limited instructions granted using Garmin Express.  I’m not surprised since the average consumer can barely follow instructions.   
I’ll try calling support tomorrow if you’re out of ideas.  You seem to be the only one who helps here and I appreciate your support even if it is unsuccessful.  

Well they will confirm your subscription level, that may be the issue, as if you're entitled to Canada they can check there's not an issue at their end. Good luck and let us know how you get on as it's a strange one.