What parties would the US have if it switched to proportional representation?

[Antonio the Sixth]

I think parties wouldn't organize solely based on ideological lines. Ideology has always been a minor factor in US history. American politics are, and have always been founded primarily on communities of interests (otherwise called lobbies, factions, or however you want), ie groups of people with a common trait (which might be ethnic, gendered, economic, professional, or based on a person's activities). I think a multi-party US is very likely to see a "black" party, a "hispanic" party, a "religious" party (or several), and many other stuffs of the kind.