Also, you list all counties in many states as having Catholics as the largest denomination. That is probably true, but do they actually make up the majority? I'm sure if you add together all the protestant sects(Episcopalians, Baptists, etc.) you will find that they outnumber the Catholics.
Episcopalians and Baptists are as different from each other as they are different from Catholics.
It would be appropriate to place the "mainline" protestants together. That includes the Episcopalians, Methodists, Presbyterians, UCCers, much of the Lutheran groups, as well as some smaller denominations. They all share very similar theology, but differ primarily on their polity, or interal governance.
