The immigrants to America are mostly from Latin America. They come because they are starving or fear for their lives at home. Most of them desperately WANT to assimilate and become Americans ASAP.
This is also the case with most immigrants into Europe, but there is a far greater proportion from Muslim countries and/or Eastern European countries that brazenly and openly want to impose their religion (worst cases in F, B and NL), or exploit the (relatively) generous government help to the disadvantaged. Keep in mind that European countries are small and compact compared to the USA. If there is a problem in San Diego, it wont necessarily stir up public sentiment in Philadelphia. In a country like France or Belgium or even Germany, anything that happens anywhere is automatically local, and makes national headlines within hours or less. Our extremist right in the USA needs a Fox Noise to make them think that people are in danger when they arent. In European countries, things that happen anywhere within, or even close to national borders are considered local. Welfare scam artists from countries like Romania are even legally there, as they are EU citizens. They cant be refused entry, and the western Europeans hate it because their taxes pay for it, and their own retirement benefits suffer.
My wife worked as a social worker for decades in Germany, and the Government gives her a pension of all of 850 a month. I still work, and make enough after taxes that it doesnt matter, but what about all the Germans NOT married to people in my position? The right wing in Europe has been handed a lot of low-hanging fruit that the US right wing has had to manufacture out of thin air.