For a couple of reasons.

One is that America is exceptional. It's a huge country with massive wealth, resources, and land. It fundamentally lacks the back-pressures that some other countries have against immigration - in fact, it currently has a declining birthrate amongst its native populace and needs labor-age people to backstop an economic inversion.

The other, regarding ICE specifically, is simple trust. People know that the executive branch is, at this time, extremely white-supremacist-adjacent if not just actual white supremacists (Stephen Miller is currently the White House Deputy Chief of Staff for Policy), so any claimed purpose for immigration crackdowns is fighting an uphill battle against the presumption that (a) the actual reason is racial segregation (you'll note a disproportionate enforcement on Latinos as opposed to native Germans or Italians or Slovakians) and (b) this administration will not treat people in its care humanely (because they don't follow rules as a general principle).

(a) is the larger "national identity" issue that makes it difficult to build a coherent national immigration policy (because even some good ideas meet an uphill battle against "Does that stop us from serving as the keepers of the tired, the poor, the huddled masses yearning to breathe free?"). But what you're likely observing is (b); American intelligentsia is looking at current events out their window and hearing the echoes of clergy in Europe before and during World War II reading from the book of Exodus and asking their congregation "Who are today's midwives?"