Calling the US voting system "modern" is a bit of a stretch - it's been around for a few centuries now. Given that quite a few other countries use voting systems that help alleviate the US "two party" problem, it's not like there aren't more up-to-date already-tested alternatives out there, too. (http://en.wikipedia.org/wiki/Two-party_system#Causes is a decent starter; I've spent a few years avoiding politics so I'd just be parroting others if I recommended anything specific :))