Probably won’t matter much unless your Singapore school is significantly weaker/less prestigious/rigorous than your US school, and even then it probably won’t matter if you do great there. If your Singapore school is “better” than your US school, doing great there might even help your cause–there are some terrific schools in Singapore.
This will depend to some degree on the policies of the colleges to which you apply–there’s no universal policy. That said, I don’t think you’ll be treated as an international at many (if any) top schools.