As long as they have an email and SSN, there would be no problem running a credit check on a potential tenant overseas. I've dealt with a few of these tenants, and always used TenantMagic.
I would note, however, that a credit check alone is not sufficient for screening a tenant. Be sure to find criminal reports, eviction reports, sex offender, etc. People are able to buy fake credit reports easily, so the best way to stop that is to use programs like TenantMagic to verify their identities.
But yes, it is certainly possible (and just as easy as if they were here) to perform credit checks on tenants overseas.