In the past Candian dollars were worth around $.65 so they were not well received in the US. I have seen signs along the interstate saying Canadian dollars accepted here.

When we were down in Old Mehico, their eyes lit up when you pulled out a dollar.

At the Maine / Canadian border. People were streaming out of Canada to shop at a huge Walmart.

Likewise along the Mexican border, Mexicans were streaming in to buy what? Pampers of all things. I also saw ancient battered Mexican pick up trucks with cardboard piled as high as it could go, headed back to the border. I think they use it to build houses there.