The immigration policy of the United States is largely shaped by the visa program. This program essentially gives foreigners permission to enter the united states, as long as they meet very strict requirements. Anyone wishing to obtain a Visa to enter the US may have to wait for up to 90 days or more, depending on the circumstances.
The Visa Waiver program allows citizens of certain countries to freely travel to the United States without having to go through the rigorous Visa program. Currently only 38 countries have been selected for the Visa waiver program, the large majority of these countries are either European or the population is comprised largely of European descent, with the exception of a few south american and eastern Asian countries.
This fact has caused some to question the intentions of the Visa waiver program, accusing it of playing favorites by selectively allowing predominantly European travelers to enter the United States. Many have called for the Visa Waiver program to be modified to allow for people from all backgrounds and parts of the world to receive equal opportunity to enter the United States.
However Republicans are actually moving in the opposite direction in terms of allowing more diverse foreigners to travel to the United States. A new bill introduced in Congress calls for a registry which targets people of middle eastern backgrounds from entering the US. Essentially it would ban citizens who have links to countries like Iran, Syria, or Iraq from entering the country.
This is in light of a so called Muslim ban that President-elect Donald Trump called for during his campaign trail. This has caused many to question the constitutionality of this proposed Muslim ban. Additionally under President Donald Trump there would be increased scrutiny for Mexican immigrants as well.