I think the ISIS comparisons are kinda like comparing the behavior of Russian troops in Ukraine with say rather more isolated bad incidents of British troops in Northern Ireland or US troops in Afghanistan, it's rather superficial and at a completely different scale. I mean the baseline/regular beliefs in countries where ISIS became popular are pretty ****ed up by western standards let alone the extremist ones!
As for mainstream media like Fox news etc.. that would be like blaming CNN for the black guy who decided to drive his truck at a load of white people, this guy was influenced by more than Tucker Carlson - rather it was the worst of 4Chan, /pol/ etc. he apparently blames Jews for non-white immigration or something - that's not the sort of thing you'd get from US evening news etc..
No its not on US evening news but the "role" of Jews in the Great Replacement is well known in these circles and Tucker does like to use "replacement" rhetoric in his shows. It is also part of QAnon which is another not so fringe (anymore) movement on the right wing of US politics. Funny that much of the lunacy on 4Chan has seeped its way into the mainstream of US politics now.
No one is saying Fox News is to blame for the growing divide and extremism in US politics but it has and is playing its part.
The ISIS comparison works better for the evangelical Christianity in the US which is gaining power, especially now with its control of the SC.