Ageism: Why can't younger people vote? Because they don't have valid opinions? Some adults don't have valid opinions. This seems to affect our dramatically in our modern era, as many of our older folks are still around and skewing the generational differences towards conservatism.
Classism: Why do we feel it necessary to have a political class at all? Bush Sr., Mr. Clinton, Bush Jr., Obama, (Ms. Clinton?). To me, it feels weird even asking these people to have differing views. They're all apart of the council on foreign relations (https://en.wikipedia.org/wiki/Members_of_the_Council_on_Fore...). Control+F either Clinton or Bush. This in my opinion, is why we won't change any neo-con/neo-lib policies anytime soon. Expect less worker rights, more outsourcing, more free trade, more deficits, and more protection of institutions deemed too big to fail (impossible in classical capitalism but not the crony kind).
Apathy: The US has killed many people in Iraq since 2003. If you crunch one version of account, it works out to 16 people every day, for 20 years. Yet most Americans are more concerned with their own internal matters. This seems like it could be extended to anything being committed outside of the US to other humans, including torture, enslavement, anything. The American people have already shown that if their bellies are full, then it doesn't matter how many people their government kills. How can anyone fix this?
Anyway, this to me seems like the major hurdles we all need to get over...