We also have contractors who are not U.S. residents but are U.S. citizens.  So they need 1099s.  It's very annoying that QB does not allow entry of foreign addresses when that is the address we use to mail them documents including 1099s.  I understand you do not have electronic filing of these 1099s, but you should still allow your customers to enter the information and prepare the 1099s as part of your services; then just flag the 1099 as one that must be mailed to IRS.  The workarounds that we use are either to ask the contractor for a second address in the U.S. that may be used, usually a relative.  The other is our own office address.  In both cases we enter "℅"  (in care of) to keep things clear.  It's still extra work, but less extra work than the suggestion above.