Possible to allow International addresses for billing only?

Hi,

If your question is "Can I have only USA in the "country" field of the shipping address but all hte countries for the billing address?", then no.
However, you can have all the countries for both types of address and use the "zone" restriction setting of your shipping methods to only allow shipping to the USA by selecting that country zone in that option.
After entering a shipping address outside the USA and reaching the shipping methods selection, the customer would get an error message saying that no shipping methods are available for his location.