The whole birther thing is dog-whistle code for racists. It seems there are some people dumm enough to believe it's really true, which is embarrassing for all concerned. Almost all concerned are in or embrace the Republican party, naturally, because the dog-whistle portion is essentially anti-Obama.
There is a legitimate political stance that we shouldn't do anything too expensive right now to try and counter climate change. It is short-sighted and selfish, and not a position I would take. But it is understandable: if you really don't care what happens fifty years from now (most likely because you will be dead), why spend our money right now to try and help the next generation but one? But no politician advocates for this stance, probably because they would look short-sighted and selfish. Instead, they all argue climate change denial: it's not really getting warmer, sea levels aren't rising, and God runs everything so the idea that man could change the weather is blasphemous. We can see the world getting warmer, watch the sea levels rise, but reality doesn't count somehow. Again, this is mostly a Republican population, because the Republican party seeks to commandeer the religious nutcases as a voting bloc.
Childhood vaccinations and the first visible symptoms of autism happen at about the same time. Correlation is not causation, but it's not surprising that somebody would form the hypothesis that vaccination sometimes causes autism. So scientists test the hypothesis and conclusively prove that vaccination does not cause autism. There are people who don't believe "the government" can ever do anything right, so if "the government" says vaccine is safe and you have to vaccinate your child, then by god, they're not going to agree. The Republican party actually wants these people as voters, so Republican politicians are the ones appearing on national TV and lying about vaccines.
The US has appalling rates of teenage pregnancy and abortion. If people really wanted to change this situation, they could do it. Reduce the number of abortions by 80% or 90%? Yes, it's doable. It would involve comprehensive sex education. It would mean effective long-term contraception being made available free or at very low cost to teenagers and poor people. It would mean good quality healthcare being made available to all women. Instead, the "pro-life" movement is only interested in controlling other people's sex lives. Their principal objective is to make abortion illegal (which will probably have a negligible effect on the number of abortions performed, but will certainly result in suffering and death for many women). Meanwhile, they actively reduce access to education, contraception and healthcare for teenagers and women, thus increasing the number of abortions that occur. Naturally enough, the political party that embraces this stupid, immoral movement (probably because of the religious component) is the Republicans.
And on and on...