The Roman Catholic Church is unlikely to ever do the things that it would have to do to stop this hemorrhage, because it would involve too many changes to the structure of the church, and reversals of positions that it has long held.
I don't think that is true at all. If that were the case then we'd have bled out centuries ago. There is always waxing and waning going on.
I think Robb has the best point so far. My sister and daughter, both living in the south, both raising children alone, both headed for the closest Baptist Church because that is where they can get the social support that they crave...there's little if any thought toward doctrinal issues at all. It appears that my sister will be going back to the Catholic Church. I don't see that happening with my daughter...ever...unless she were to leave the south.
If you reject Jeremy's explanation, then it means the Catholic Church can't act in America to change the process.
Robb's explanation is correct, but the Subjective Element in social processes cannot be denied.
I would like to think that the Roman Catholic leadership could take some steps to stem ore reverse the hemorrhage. If that's true, then the fact it hasn't done this means that the RC leadership has failed to take the steps because of serious shortnesses on its own part.
The facts that (1)Protestants have some important things in common with U.S. Orthodox, like married priests, allowance of some contraceptives, more democratic governance of parish life, etc., and
(2) Catholics complain about these issues in the RC as an institution
suggests from our Orthodox perspective that a serious part of the problem is due to the R.C. as an institution.
Still, this does not mean that Orthodox are immune from the same social conditions pulling people away from R.Catholicism, like feeling a lack of a need for strong spirituality, and the fact that RCs and Orthodox are a minority.
It could be true that consumerism, competitive capitalism, republican democracy fit best with what we see in the evangelical movement, the idea that each person's conflicting interpretation of the Bible is right. Populist democracy fits in too, because of the movement's simplicity. Probably Agnoticism, the evangelical movement, and moderately-traditional Protestantism, are seen as the most "American".
Fortunately, democracy allows for diversity, so there will always be a few Christians who think outside the box, and immigrants in a few big cities...
To put it another way, at least Alaska will stay Orthodox:

(I hope this is a joke)