Numerous American nonprofit organizations act abroad with significant influences in such areas as charities and aids，ideological and cultural disseminations，and professional and associational coordination. These overseas activities and their influences are affected mostly positively by domestic economic，political，social，and cultural foundations as follows：economically，the tremendous size of economy，the nonprofits-friendly tax and regulation systems，the high average income level，and a globally magnetic market；politically，easy registration and tax exemption status acquisition，institutionalized nonprofits management systems，strong governing capacity and the willingness to export its governance model；socially，multitudinous autonomous organizations，smooth elite movement mechanisms，open and transparent oversight mechanisms，and diverse resident groups；culturally，the long tradition of freedom of association，education and employment systems that value nonprofits services，and a globally oriented teaching and research system. New changes of American fundamentals in the 21st century are leading to new influences that worth further discussion.