What term describes the belief that current inhabitants big an area are better than incoming immigrants

Americans who were against the immigration were Nativists  (they continued the policy of choosing Native citizens as opposed to the immigrants).

The hostility to the newcomers generally started in many nations as a  matter of cultural, national and religious integrity. Their movement can even allow cultural survival. This term Nativist went known in 1854, at the time they formed an American party, which was particularly opposed to the migration of Irish Catholics.