First bit to understand; the US is split between the coasts and the bit in the middle. The bit in the middle is massive generalisation coming up religious and unexposed to the rest of the world and the coasts are a lot more used to immigration and diversity. Its a huge divide. The coasts are traditionally vote Democrat, the centre votes Republican.
Second bit; every election generally is either characterised by a focus on foreign or domestic policy. Foreign policy focus generally comes at times of prosperity and war. Domestic policy generally comes in times of economic hardship. At the moment the issue is the economy so America is very inward looking. The rest of the world tends to become a lot less important. It might not be something they can afford to do in 2012 though as technology and world economics mean its more difficult for the US to be isolationist - not that it stops some politicians trying.
The Democrats are nothing like Labour. Labour and socialism is looked upon suspiciously by Americans as being authoritative and controlling. Unions are regarded as communist. Its worth pointing out that during the height of the Cold War, talk about unions could have got you arrested in the US as they had a witch hunt against anyone expressing views to give workers rights due to their paranoia about the Soviet Union. I wouldn't say that the Democrats were like the Coalition - the Coalition is still too liberal leaning - it is still a big deal for Obama to make pro-gay comments, whereas even though some MPs can be backward on that issue, they would be expected to be more PC. The Democrats probably sit slight to the right of the Tories on their own.
As for the Republicans; well they are suffering from something of a crises of identity at the moment and are being pulled by one half of the party who were generally more interested in economics and one half of the party being crazy lunacy religious fundamentalists who want to blow the rest of the world up for not obeying them (And frankly I'm not exaggerating when I say that).
Romney is also a bit of an outsider due to his religion. He's a mormon. Ignorance does make some voters suspicious of him. But he probably sits in the more to the middle of the Republican Godsquad compared to a lot of other party members and voters. He was Governor of Massachusetts so he is a Republican with appeal to the more liberal elements of US society. Republicans generally want less government involvement in every day affairs than the Democrats - which is why they are often supported by big business. This is where Romney really fits in. His father was a business man and politician and he followed this.
As a whole its definitely correct to say the Republicans are to the right of the BNP; how far to the right generally is proportionate to how much you believe in creationism - some members of the party would have a lot to talk about with a member of the Taliban at a dinner party.
But this split in the party is also their big weakness. There are some traditional Republicans who are alarmed by the extreme right of the party. Romney's comments about the Olympics were telling and have troubled Americans about his lack of diplomacy and inability to deal abroad - something thats really important especially at the moment when the economy is the big issue. His appeal to the more liberal areas of America will be down to how he is trusted with business and how scared they are of the Looney Tunes; if they think he's too much of a diplomatic liability or they think the Looney Tunes have too much power/influence it could be Romney's downfall.
With regard to economics, amount of government intervention is the key point. The idea of the American Dream that is reward through hard work is the underlying principle. Therefore if you don't deserve reward if you don't put in the effort. Having benefits undermines this work ethic according to Americans and it makes you dependant on the state rather than self sufficient. Its a fine mentality to have if you have status and money, not so much if you don't. The hard work ethic is reflected in attitudes to employment law and legislation - workers have far fewer rights than in the EU. The US argue that this makes their labour market more flexible as they can hire and fire at will and not have to go through due process like here. Its actually proved to be fairly true; although the US suffered a lot more unemployment, they've been able to recover from that a lot more as its not so much of a commitment for an employer to recruit someone new. This is an issue that has been high on the agenda; a couple of the Republican candidates for the presidency took a very strong line on this and have track records of eroding the already poor rights of workers even more in the States they represent. Its popular with employers and business.
Those at the bottom of the pile, don't have much say in politics though. Historically blacks and the working class were far less likely to vote at all than the middle classes; in part because the candidates don't even campaign on issues that benefit them and instead pander to the middle classes. Its a little bit different with Obama; his colour was a big issue as it represented a break from this - he'll be judged this time on whether he has actually delivered. Obama's problem is more likely to be getting black voters to just turn out to vote this time especially in the swing states of the South like Florida if there has been some disillusionment over this term - particularly since it has been a period of weakness economically.
So Obamacare is a HUGE issue.
Then the parties have a few issues which are particularly important and we don't understand at all here; gun law and abortion being the two that spring most to mind. Here, all reason is very often lost in a sea of bollocks and hysteria. damn straight I don't get these issues!
And finally, in this rather crap summary of US politics there is presentation over substance. The slick media campaign over anything actually vaguely political. Romney is 65. Obama is 51. Since JFK, the candidate who was younger and looked better on TV has won.
Romney needs to invest in some JustForMen.