They aren't exactly the same interests. Because real preferences are multidimensional and the US electoral system has strong structural features which promote a two-party system (with differences that lie on a single dimension), for people whose most important issues don't lie on the axis of variation between the parties, they can seem similar, but they don't represent the exact same interests.
What we're 'allowed' to do is basically anything that keeps us too occupied to overthrow the ruling class...
You're just rationalizing.
When it comes to politics HN is conspiracy kiddie central. The US has a real two party system on top of dozens of state and local jurisdictions, all part of a larger checks and balance system. Sadly, I see a lot of criticism from Chinese and Russians who want to badly equate their broken autocratic system with our system, and that just isn't correct.
The US is NOT the paragon of democracy.
In a two party system, the small extremists can't win enough seats to be of note. That's a feature, not a bug. As we have seen many times before in the US's history, small movements move up through the party primary process. So you have the best of both worlds: a lack of easy access to government by extremists and a path to changing one of the larger parties via the very democratic primary system.
I don't think the US system is perfect, but its good; it solves a lot of problems of governing very nicely. The framers did their homework. The idea that Euro-style parliamentary systems are unequivocal better is a questionable premise, especially since it did nothing to stop the rise of Nazism in Germany (or even protect the lives of the Jewish minority) and other lesser but significant social failures (Greece's white supremacist Golden Dawn winning 22 seats in parliament recently for example.)
Not to mention, the States are fairly autonomous by Euro standards, so the state level legislature/courts/constitution are actually important and not just the bureaucratic/administrative arm of the national government. That gives a lot more local representation than the generally top-down decrees of Euro states - and that's on top of whatever the hell the EU is and all of its trans-national top-down decrees.
In the USA's particular case, you have 2 parties which, despite the claimed differences, wind up representing the exact same interests. Obama, far from being a reversal of Bush's policies, continued and expanded all of them.
And no matter who comes into power, will likely expand on every repressive law and strategy that's in effect right now.