Many things already are, but it's not an environmental choice but a boycott so it's not about being overseas or not anyways. Why support a country that's actively hostile to you, ya know?

In practical terms it tends to be buying the strawberries from Mexico instead of California for example. The grocery stores literally have little maple leaf symbols on the prices to help, and little tariff symbols as well. Plus people aren't traveling to the US as that's a way of not "buying" from there too, often opting to travel within that country or overseas.