non-proportional elections are not what makes US democracy unfair. The real problem is that US has bunch of laws which seem specifically designed to deter poor black people from voting: the lack of government issued ID (which in my country you can get for free), not enough polling stations, forcing people wanting to vote to stand in line for HOURS, gerrymandering, or even the fact that US elections are held on work days instead of holidays (making it harder for people who work two jobs to find a time to vote).

There are multiple axes by which a democracy can be unfair. It's possible to have a fully enfranchised population, but let a constituency of five people determine one delegate, while a constituency of five million people determines another.