There isn't much I will diagree with in your post. It is well thought out and nearly [if not] entirely on point.

I want to caution you on one point in fact however which makes a difference when we talk about idealogies and where they came from and why:

The real reason, aside from anything anyone will ever tell you (but I suspect you may already know), is that the United States was not formed just to promote religious freedom and get representation. Sure, we didn't want to pay taxes to mean old King George. We abhorred the taxes imposed by Parliament. But more importantly, the spectre of continued English, King -rule threatenened the interests of moneyed, propertied whites. The fact that freedoms became part of the reasoning was a bit of subterfuge really on the part of our Statesmen; they had to make it attractive to the everyman in order to get them to do the fighting for them. You didn't see Ben Franklin or Patrick Henry painted in battlefield artworks brandishing muskets, they were newsmen and landowners, respectively and they got common people to fight for them.

Interestingly enough, one of the first things politicised was divorce, not typically legal at the time. Any woman who considered herself a Patriot was granted a divorce from her Loyalist husband if so desired. Native Americans were not really sympathetic to the American rebels or British (fearing reprisals from either), but the Iroquois did join against the rebels hoping to halt American expansion into their lands. As time went on, various tribes sided with one or the other; unfortunately they were sort of in a no win scenario with either. When the Iroquios fled to Canada, they found after the war was over that the British had ceded land they didn't control to America. So the problems with NAs started early. Blacks also were politicised early on, the British trying to encourage slave revolts, but they had to be careful doing this lest their own slave trade be endangered or the social order be disrupted by revolts (West Indies) by their own slaves. Interesting times, and it was later easy to demonise Indians (as Columbus called them, but he was an idiot of the highest order).

So really, we started out as unified then broke apart so to speak. There are always some who think theyhave a better idea or a better way of doing things. So we had multiple parties; I think every possible political name combination has been used to describe groups and their political style of representation. Patriots, Whigs, Americans - whatever.

I am with you that there is very little difference between Democrats and Republicans. Perhaps years ago there was but now it is just about power and control. That is where the demonisation comes in. They have to demonise each other so they can get into power. Fortunately our system, albeit a very imperfect one, kepps the pendulum swinging, but it never stays in the middle lest the middle be also demonised. Libertarians don't have a chance of winning because the money machines (MIC) are well entrenched in conventional D vs. R politics.

Abortion should never be allowed to be a part of politics. It is a moral issue rather than either a legal or political one. The easiest way to make the abortion issue go away is for stupid women to keep their legs closed. Simple as that. Yes, oversimplification and the feminazis will bitch about it (ever notice they never much look like they'd ever need an abortion?) but in this day and age there is no excuse for an unwanted pregnancy in most cases, rape aside. Rape is often used as a crutch in support of abortion, but rape pregnancies are difficult to actually account for. I agree that abortion should be rare, although legal.

Your example of Republicans and Christians is actually an excellent example, but that is not to say there aren't Christian Democrats because there are. Being Methodist, I see both sides. One area where there seems to be a lot of disagreement is where alcohol is concerned. Methodism does not allow alcohol, either for communal wine or events such as Beef and Beer as a fundraiser with any other festivity. Interestingly, Catholics (despite the protestations of some Methodists and Other Protestants) are indeed Christians and let the alcohol flow freely for the aforementioned events - gambling as well! Why do the Methodists not allow drinking? Perhaps because John Wesley was a bit of a kook with an estranged wife and he felt it should be forbidden (although emphasis was given to "strong drink"). But Protestants and Catholics are Christian, and according to American law, both drink and gambling are legal. Abortion only adds to the confusion because of traditional church stances. Abortion is nothing more than a political football. Candidates have to be careful how they speak of it for fear alienating their base or in appealing to their opposition for support.
  Abortion, voter IDs, welfare, health care, immigration are all issues that all are largely agreed on but are turned into bargaining chips for political support.

Republicans: Pro-business and for people to make their own way rather than having government provide. Allow the marketplace, free enterprise and competition work to strike the balances.

Democrats: Pro-Union, have the government force businesses (taxes) to help take care of what people may not be able to do for themselves, the government will provide the rest. The government will oversee and regulate so that businesses cannot control the money. Claim to be for the "little guy"
  It may be cohesive, but there are elements about the Libertarian Aprty that limit its viability. Their stance on separation of church and state is not supported by the Constitution, rather that reference was a reassurance to the Danbury Baptist Association that the United States could not form a national church or interfere with their manner of worship. This has been construed to mean Freedom from Religion, which is what some prefer but is not the within context of the letter.

Open immigration is another stance they tend toward, but that will never fly with the American people, neither will neutrality and I doubt non interventionism.
  Been that way pretty much forever, but more glaring since the second world war.
  For a measure of the population, that debate would be lost on them. They are too busy watching American Idol, Britain's got Talent, Survivor and Modern Family. It is not the watching of those programmes that is the problem, it is that those programmes take priority over other aspects of their lives. They tend to be those who vote on "hot-button" issues alone, such as same-sex marriage and abortion rights. Presented with valid arguments either way, they respond only in self-convenience or just to beat the person with whom they might disagree. Low information voters is all they are. They tend to be the loudmouth sign and banner wavers. In many cases, when presented with the oppositions platform, they may not even know their own candidate is opposed to that platform. Unfortunately, there are too many of them in contrast to the other people who are relatively aware of what is going on in the country or at least make a concerted effort to be informed.

I'd submit a better informed electorate does not vote barack hussein obama as their "first black preseident"; for them, it was nothing more than a milestone. That is not to say that their only choice at that point was Romney, but obama has proven to be not the best guy to lead America. His supporters are getting harder to find every day. The low information voters are going to want another milestone in a female president. If the female I am thinking of is who they want to vote for, I sincerely hope theirs is a failed endeavor.