Ah yes, the US two-party system.

The Democratic and Republican Party agree that it is in their interest to retain the two-party system induced from FPTP voting and the Electoral College and that is unlikely to change through reform from my point of view.

Some of the predominant ideologies in the US:

https://www.wikiwand.com/en/Democratic_socialism (PSL)

https://www.wikiwand.com/en/Liberal_conservatism (GOP)

https://www.wikiwand.com/en/Libertarianism_in_the_United_Sta... (US Libertarians)

https://www.wikiwand.com/en/Social_democracy (DSA)

https://www.wikiwand.com/en/Social_liberalism (DEM)

etc.