Sorry I should have been more clear, got late last night.
So if you get prescribed here in the US yes you definitely get your script filled here in the US. In Canada and US once you give the script to pharmacy they print a medication label and attach to meds which becomes your prescription. You can take that anywhere in the world, the only place extra steps are necessary is Australia you have to get on their site and download this form and submit application to bring in schedule III.
Its easy to do just a process. You also have to have a letter of necessity for Australia but thats the only place.
So Canada wants you to keep those prescriptions meds and the prescription length for those meds to 90 days or less.
Some of our guys have service center mailboxes here that sign for packages, so we have a decent amount of clients who reside or visit both places, US and Canada
Hope this helps.