I agree that refugees are a special case.
https://worldrelief.org/what-is-a-refugee/
In US law, the legal definition is someone who is outside the United States, seeking to be admitted, who fits this description:What is a refugee?
Refugees are people who have been forced to flee their countries because of violence or other persecution on account of their race, religion, political opinion or other reasons under international law.
Refugees entering the United States have already been vetted, and the United States government has already determined that:8 U.S.C. § 1101(a)(42) wrote:who is unable or unwilling to return to, and is unable or unwilling to avail himself or herself of the protection of, that country because of persecution or a well-founded fear of persecution on account of race, religion, nationality, membership in a particular social group, or political opinion
1. They have a credible fear of persecution.
2. They are not a threat to us.
3. They have not persecuted others.
There are about 35-40 million refugees in the world. Only a small fraction are ever offered third-country resettlement. Most years, well under 1% of refugees are resettled at all.
Under Obama, about 74,000 refugees were admitted in 2009. At the time, that was roughly 0.28 % of the world's refugees. Since 1995, most years have been well under 100,000 refugees.
That's on the order of 2% - 4% of all legal immigrants to the United States.