There are a lot of reasons for that. Most of them start with FPTP voting, which ultimately leads to less parties being present in a parliament and less democratic representation ofthe actual will of the people, which in turn leads to radicalisation, which in turn leads to the inability to compromise because this would look "weak" for the more radicalized people in the party.

Another problem is the disparity between population and representation in US politics This is based on the founding fathers' dislike of people living in cities due to their experience with London back in the time. They got it wrong for the wrong reasons, but US politics still considers even the most outdated notions of the founding fathers as gospel and won't fix the most glaring issues that plague US politics.