If one is only an American Citizen, they are still considered Citizens of the United States regardless of where they live (though they may be legal "residents" of other countries their "citizenship"...
Native American U.S. citizenship is a complex issue involving hundreds of tribes and Indian organizations. The earliest recorded date of Native Americans becoming U.S. citizens was in 1831 when the...
Be careful of where you get your information from, legislation is constantly changing; recently it has been more toward being easier to be born abroad. If YOU (grandparent) are American (born abroad...