Part of it is cultural due to the origins of our country. We are mostly a country of immigrants. On the base of the Statue of Liberty is a poem “The New Colossus” which says:

Not like the brazen giant of Greek fame, With conquering limbs astride from land to land; Here at our sea-washed, sunset gates shall stand A mighty woman with a torch, whose flame Is the imprisoned lightning, and her name Mother of Exiles. From her beacon-hand Glows world-wide welcome; her mild eyes command The air-bridged harbor that twin cities frame.

"Keep, ancient lands, your storied pomp!" cries she With silent lips. "Give me your tired, your poor, Your huddled masses yearning to breathe free, The wretched refuse of your teeming shore. Send these, the homeless, tempest-tost to me, I lift my lamp beside the golden door!"

There are reasons beyond the cultural history or being a country of immigrants. Much of the innovation of the US over it’s history is due to immigrants. From modern physics, the telephone, the Internet, mRNA vaccines, etc. 46% of Fortune 500 companies were founded by Immigrants or their children. 44% of billion dollar tech startups are immigrants.

Without immigration, the US would have negative population growth, which is economically probably a disaster. We’d have to achieve impossible levels of productivity to support the larger aging populations. Additionally the job losses you mention are mostly in Technology, Finance and Government… sectors that aren’t exactly dominated by immigrant labor.

Being protectionist doesn’t typically work out from a cost and labor perspective. We already have shortages in farming, construction and health care labor, which are often populated by immigrants. So overall, we’d have more unfilled positions, which would result in higher prices, etc. Native born Americans just don’t seem to want those jobs.