Maybe, but I think that the process of various factions trying to rise to the top would take a long time. Left to their own devices, as they would be, they could easily spend the next 100 years killing each other. The tribal hatreds are deep, and will be exacerbated by the loss of the economy they have taken for granted up until now.
While some may respond to Islam’s “promise”, Islam is going to be competing with all kinds of demagoguery and leftist utopias. In this country, at least, I don’t see it having much success.
My bigger concern lies to our south. Mexico is falling apart right now. A collapse in the US would seal their fate, and the chaos would inevitably go north. Any united message stemming from that mess would find a very receptive audience throughout this country.
Oh, and you are right about the southeast. I generally think of the southeast as being non-coastal, for cultural reasons.
Mexico (and the Mexico Norte within our own borders) are a wild card. A broke and hungry USA would destroy them. But, they are strong Catholics down there. Would they fall back on their faith, or abandon it to turn the American west into some Mad Max wasteland?
As for the leftists, they will not survive the collapse.
First, they cannot exist without modern conveniences (except for a few hippies). They exist because of The Thin Chrome Line, which is the ability to pretend to be back-to-basics and down-to-Earth as long as someone else is keeping the electricity, water, petro-chemicals, pharmaceuticals, and communications infrastructure working for them. These are people that think that not having a Starbucks within 10 minutes drive is the apocalypse. These are people who have a bicycle in the garage and drive an SUV to the gym to work out. They are walking contradictions.
Second, when the SHTF, the good Americans who worked hard and paid their taxes and raised their own kids and just wanted to be left alone are going to want some payback—big time—from these jackals that ruined America and doomed the human race to a thousand years of hell.