> evangelical Christianity has been one of the primary tools used to advance and justify segregation and slavery throughout western history
This is right if you say "America" instead of "the west". And then you're talking about a timescale of maybe 200 years, tops.
But when you say "the west" you're talking about a longer history of Christianity in Europe. You're talking about the Catholic Church, the Protestant Reformation, all that.
And on long historical timescales, Christianity's record is quite a bit more complicated than that. You can certainly associate it with various sins -- it suppressed the pagans, it launched the crusades, in Spain it justified conquest in the New World, and (though it was its own team) it often sided with royalty and aristocracy. And yet it was not an essentially "pro-slavery" religion. That would be to project relatively recent American evangelicalism backwards onto the rest of Christianity in a totally ahistorical way.
> There was notable involvement in the abolitionist movement among northern Protestants, and civil rights activism among catholics, Jews, and northern Protestants - but acting as though that is in any way representative of American religion is missing 99% of the history.
There used to be a phrase, "mainline Protestant", used to distinguish "normal" Protestants from evangelicals. They're dying now, but those churches used to have huge membership. The kind of Christianity that was "centered" in the past in America (at least in the North) was //not at all// the southern Evangelical variety that so often claims the word "Christian" these days. You're missing the amount of change that has occurred. The Evangelicals were "weird".
Your discussion of "Catholics and Jews" in the context of "abolitionism" is also confused. Catholics and Jews were not //totally absent// from America at that time, but it really wasn't until later that they came over in large numbers. Like, Irish were just arriving around the time of the Civil War (and hadn't even won respect for themselves yet, let alone taking up the political cause of others), and Jews started to really show up later around the turn of the century. You're ignoring the timeline of immigration.
Finally -- your whole dichotomy of "American religion" vs... atheism(?) is confused. In the past, atheism was taboo -- "everyone" was religious to some extent -- and //even so// things like the Civil War happened. Why? Because it was religion that //animated// those movements, particularly within the emerging "white" ethnic group (whose material interests they did not necessarily serve in an obvious way).
Mostly, American history has not been "religious people vs nonreligious people". It's been different kinds of religious people fighting over the contents of their religions. Mostly, the battle lines have been drawn right //through// Christianity in America.