Adding Canada Shipping, blocks US addresses, customers cannot buy anything

Based in the US, when I add an additional shipping channel (in this case Canada), some of my USA customers, even return customers are not able to purchase from me because not because shopify says the address is not valid. Even though the address is auto-populated. Once I remove the Canadian shipping channel, the address is accepted. I have tested this myself. I want to shipping to Canada but I need everything to function properly for my US customers as well? Anyone else have this issue, is there a fix?