Yep…although the term “wedge issue” might need a definition. If so, let me know.
But I’d say somewhere during my adult lifetime the discussion of immigration (as in levels of, vs. other aspects tied up with the topic) went from “oh, I see they are thinking of passing a law to XYZ immigration, I am generally [for | against] that”, to "Arrggg…immigration!!! Why won’t you see things my way!!! Arrgghhhh!!!".
This switch may have occurred as result of Immigration Reform and Control Act of 1986 under Reagan, but I’d have to do a little more digging. I was in college then and probably less concerned with current affairs, but I definitely don’t remember any heated arguments or demonstration or whatever. But with regard to immigration vis-s-vis being a wedge issue, I’d say somewhere in early '90s was a tipping point.
As to “Civics, citizenship, and the Constitution…” etc., again, I was taught all this growing up in suburban Chicago while it was being run by the Daley Machine, i.e. when being a gangster was a respectable living. It came from al;l sides: parents, teachers, neighbors, clubs & organizations (e.g. BSA, Kiwanis, AMVets, etc.), TV and Media. Informal survey of my nieces/nephews indicate about 50/50 split as to how much of this was taught/available (one couldn’t give me 1st 3 words of Preamble). So grade schools seemed to started de-emphasizing civics, etc. somewhere between 1980 and today. Maybe a result of emphasis on teaching to the test? I don’t know.
This clarification on my part won’t matter if I am interpreting your posts correctly. If so (I really don’t want to put words in your mouth) you appear to think that American (or any particular group) values are determined by asking the group at the current time “what are your values?”, in other words they are fluid and time dependent. That’s not how I see it, though…values should be fundamental to an organization, something people can count on through time, and generally static, not fluid.
It’s like making a table. And then years later, a leg busts and has to be replaced, and then a few years after that another one. And then someone lights a fire on the top of it so it needs to have a new top. Is it the same table anymore? It’s still a top with 4 legs sitting in the same place as it was, but IMO it isn’t the same thing as was originally created.
In America’s case, which was a very unique thing at the time in that it was a country founded on ideals and values and principles, not preexisting borders or by tribal, ethnic or racial uniformity, and those ideals and values and principles were laid out by our founders and framers; they are what they are. And if you were willing to move here (nowadays you have to follow a process, but not back in the day, of course) and subscribe to those values and principles, that’s what made someone an American, and what made America. (cue national anthem and tear-in-eye).