DACA and the undocumented: that's a legitimate fear. Muslin Americans and Muslins here legally: that's legitimate but I'm confident our institutions are strong enough to prevent something that blatantly unconstitutional from happening.
Many Germans said that in 1933. I know because I interviewed my grandparents before they died, and they told me so. They fled to Palestine, but many of their friends stayed behind saying, "It can't possibly get that bad." None of their friends survived.
I find it terrifying this gets down voted. We should always keep in mind what the parent said no matter who is running this or any other country. Things like that have happened several times before in history in different scales and we need to remain vigilant to prevent something like it from happening again.
It is a test of the citizenry whether such assaults on those institutions is tolerated. Korematsu v. United States is an example of how those institutions alone aren't necessarily strong enough when citizens don't really give a hoot. Korematsu is widely regarded as bad law, not case law. But until there's another test, it's speculation. And even contemplating it being tested is scary, but I think less scary than ambiguity.
The long history of the Republic. Our Institutions have failed us whether it's slavery or the Japanese internment, Jim Crow, women's rights, LGBTQ rights, the hysteria after 911. But in each case we eventually recognized our mistakes and made corrections.
You readily acknowledge "Our Institutions have failed us" multiple times, but you're arguing they can't fail us again because of "The long history" - I think you're arguing against yourself. And while this is digging further into the past, you left out The Trail of Tears from your list - an iconic example of the president ignoring the law because he can. That man is now on our $20 bill, so it seems he's been rewarded by history.
Saying injustices happen and are eventually rectified is one thing (which seems to be your argument), saying injustices can never happen again is something completely different.
What are the corrections made relating to the treatment of First Nation peoples?
The Japanese internment has already been trotted out as a precedent for creating a registry of American Muslims. That doesn't sound like recognizing our mistakes and making corrections to me.