The difference between America and the rest of the world is that America has more immigrants relative to its population and in absolute terms than any other country.
Out of curiosity, can you name a non Western country less racist than America?
This is why you see all the other vile laws against abortion and the “don’t say gay laws”… they don’t actually benefit the states at all but are a useful tool for the politicians that peddle them to stay in power.
Many people are racist/xenophobic and don't want people of other races or cultures "taking over" their neighborhoods or towns. Even those who aren't actively racist are just resistant to change on that level, because it scares them.
Like I don't want to be coy about this, the Republican Party is diametrically opposed to any kind of immigration reform that would let in more people that don't look and talk like their voters. The only policy that republicans support that might decrease their average age is anti education and anti birth control/abortion measures.
We should not continue to be surprised by this. It's what they've been saying for decades. You can't counter an irrational fear of the other with rational arguments about immigration - the racist nugget at its core just has to be nipped in the bud.