Tax calculation configuration question for foreign customers

I have a US company code which is using the tax procedure TAXUSJ. I have foreign customers that I need to calculate taxes on. How do I add the necessary tax codes so that the system can calculate taxes? Since I am using TAXUSJ, when I try to add tax codes, the system requires a tax jurisdiction code to be entered? I realize that I must be missing something somewhere.

I have foreign customers in several countries (Canada, Mexico, United Kingdom, Germany, etc.)

Any assistance will be greatly appreciated.

Greg Brown