I disagree that the loss of optimism is causative. I've lost my optimism because I've seen what we're capable of as a country and it's not reassuring.

>That cynicism means civic disengagement

By what metric? You have to go through Scandinavia, Germany, Spain, and a few Eastern european countries before you get to the US on voter turnout. Not to mention labor unions striking as a form of political protest (eg Italian labor unions striking against the Gaza war). And depression prevalence also seems to be higher in the US. Did you mean worse than Europe instead of "almost as" bad?