As for the political polarization going on in the US, that is a big issue and it doesn't help that the President trolls the liberals all the time.
Some issues are politically intractable, like abortion, neither side is ever going to convince the other side because there are good argument on both sides, it is an issue that naturally divides people. Awful as it is, the majority of people do favor the pro-choice side and the right just has to accept that, but of course they won't and politicians will use that to get them all riled up because that gets them out to vote. So the political heat on that is always turned up to high.
Gun rights is another intractable issue with good arguments on both sides and politicians again keep the heat turned up to high on it.
There are other issues like education and the environment and worker safety where there are good arguments on both sides and again the heat is always turned up to high on these.
In total all these intractable issues cause the polarization and politicians ride that polarization into office and use it to rally the troops on their behalf. It is up to the voters to realize they are being trolled by their own politicians to keep them riled up and to reject that. It is hard to do, people feel passionately about these things, emotions once engaged cannot easily be disengaged. But emotions cannot be sustained at a high level constantly, so eventually people will be worn down and turn away.
People need to engage with their brains and not their balls or guts. Recognize when a politician is attempting to rile you up emotionally and then take what they say with a big grain of salt. Listen for the rational argument and give that your attention.