The United States is a nation of immigrants. Only the Native Americans are indigenous to this continent, and at some point in their history they may also have come to this region from Asia across the Bering Strait or by some other means. In this century, consecutive waves of immigration from different parts of the world created tensions with Americans already living in this country, for they believed that the immigrants were taking their jobs, gorging the welfare roles, and somehow reducing their overall standard of living. Beginning in the 1920s, the object of the law was to favor certain kinds of immigrants and to keep out others. More immigrants were permitted from western Europe and fewer from southern and eastern Europe, and Asians were totally excluded, primarily to prohibit Chinese, Japanese, and Filipinos from acquiring U.S. citizenship.