Actually, I think that the system with "first-past-the-post" voting, tied with small voting districts is much better for representative democracy.
Yes, the one visible result is that you get only two political parties (because being third, with no prospects of winning makes smaller parties to give up). However, the two parties tend to be internally much more diverse than you get in other systems.
The system where there's a proportional representation means that the elections now become nationwide - first you count votes for each party, to determine how many seats they get, and only then you assign seats to individual candidates.
The way it is implemented in Europe gives two terrible results:
1. The leader of the party now have much more power over individual candidates, since none of them can get into the parliament on their own, they need support of the nationally-recognized party. In American system individual congressperson is free to say "fuck you" to their party leader and will still be able to win their seat in the next elections.
2. After some small party gets into the parliament they are basically powerless, they have no way of delivering on their promises to their voters, so instead they focus on "just being there" and receiving Member of Parliament salaries. Basically, small parties are just there for comic relief.