Case 1: Inter-company Sales Order Processing - International (‏1MX‏)

P.S. Tax Departure Country Need to be set as US manually to make this case work

Case 2: US Company Procure from Canadian Supplier

Case 3: US Company Sell to Canadian Customer

For Canadian Company sell to US customer, Canadian tax procedure instead of US tax calculation procedure will not be triggered, thus US tax will not be calculated.