The United States elects its members of Congress through the First Past the Post (FPTP) or Winner-Take-All electoral system. This system creates skewed results and leaves many Americans unrepresented in Congress. If you vote for a party that loses, even if by only a couple of percentage points your vote essentially didn't count.
In a proportional electoral system (PR) (there are many variations on it) as long as a certain percentage of the population (normally around 5%) in your district agrees with you someone will represent you.
Proportional Representation (PR) system allow voters to choose who they want in office rather than the lesser of two evils.
Every Vote Counts in PR.
Voters in American want choices on election day PR gives them that better than the current system.