Yep. It's called the Vatican II effect.
It seems that there are many reasons for the deterioration, and these are problems which the Orthodox in the area are also struggling with. Though based on articles I've seen, for example on the GOA website, the problems aren't isolated to the rust belt.
Agreed. The larger issue is increasing secularism, 'post-Christian' society - all of us in the West live in it. Christians of all denominations face common struggles on a greater scale beyond the serious theological differences that divide us.
It is a fact that the Rust Belt, along with the Northeast, used to be Catholic strongholds - I mean up to the mid-20th century. Vatican II, really the spirit of Vatican II, which is what it was on the ground, had a huge impact in these regions. Changes to the liturgy. Shift of focus away from 'traditional' Catholicism. Social justice emphasized; moral doctrine downplayed, neglected, revised, updated. Clergy, bishops, even laity, who opposed the new trends ostracized. Liberals packing Church leadership roles, Church institutions, schools, higher education. This part of the country has been hit about the hardest for the longest time. Pew clearing. (scandals, anyone?)
You do also see this in the Protestants: the emergence of so-called 'non-denominational' Evangelicalism replacing the older more traditional, shall we say 'Calvinist leaning'/fundamentalist' Evangelicalism, which was quite strong up to maybe the 1980s. I know little about this in the Orthodox Church and various jurisdictions, but my guess is, again, the Northeast/parts of Rust Belt would be a door to modernity, 'openness'. I don't see how Orthodoxy can resist it completely. I mean look at what Rod Dreher is saying. (I am personally looking to Orthodoxy right now as a potentially greener pasture than Catholicism in this regard (this is only one reason; it is also spiritual, change of heart) but my eyes are open. I think you notice this modernizing, pew clearing trend more in the Catholics and Protestants in the West because of their size relative to Orthodoxy. The sheer number of people in these Churches creates a sort of natural vulnerability/receptivity to a wide variety of different influences.
In a larger sense, the question for all Christians is what to do about this post-Christian culture. Do we pull out or stay in, to evangelize or not to evangelize. Papa Francis is not going be much help I fear; but he is not a bad man. I don't oppose everything he does by any means. I'll take the RCC over a lot of what is out there, even in its current dilapidated state. I still think it is the original, valid Church - as is the Orthodox (please let's not go there - off topic anyway).