The U.S. Constitution applies broadly to everyone present in the United States, including non citizens, under the principle of "personhood", guaranteeing rights like due process and equal protection (5th and 14th Amendments). However, some rights, like voting or holding office, are strictly for citizens, and the extent of protections ( like First Amendment) can vary slightly by legal status( citizen, resident, visa holder, etc.), though fundamental liberties generally hold for all. #KnowYourRights