But this whole idea of majority/minority leaders is dependent upon the idea of an oligarchy of respected parties. Of which presidential politics encourages there to be exactly two.
If the Green Party managed to get members in Congress one day, shouldn’t we then have multiple minority leaders?
There have been times in history where there have been third party members of the House of Representatives. I would suppose that each of those parties had their own leader, so you might say yes, there were multiple minority leaders. But obviously, a leader of a third party with only a small number of members generally would not carry too much clout.
Not "Presidential politics", our election system which is called "first past the post". FPTP tends towards 2 parties because neither the right or left wants to split their vote. Look at the 1912 election, Wilson got under 42%, (less than the losing rat from 1908) of the vote but a huge electoral college landslide cause the GOP vote was split, and likewise the rats won 2/3s of Congress cause TR's Progressive also ran candidates for House and state leg.
Looking at multi party proportional representation systems like in Europe, they're a disaster in my opinion. It would be terrible if we had something like that.