I believe that the problem of it all might just be the two-party system. I might sound biased, as I am a western European, but having only two parties eventually leads to polarization, and with that to radicalization. Because if you have only 2 adversaries, they will end up seeing each other as the main "enemy", and not a potential partner who simply has different views. And another reason might be that because you only have dems and reps, you do not represent other political views on the spectrum, which leads to misrepresentation, which, again, can lead to radicalization.