I have apps to be updated so I push update and little blue box pops up to say my accout not with American store I must switch over to Canadian. I'm in Canada and this has always worked what happened and how I fix it

When I open the app icon because it has updates, and hit update, a little box pops up and tells me I'm on a us store and need to switch to Canadian to purchase! How do I change this and why is this coming up