I think US politicians' failure to act effectively in the interests of US citizens is caused more by the concentration of political power than it is by bad people. The US isn't alone among developed countries in having this problem, but there are plenty of developed countries that manage to avoid it. The answer is more democratic accountability, in the form of measures such as proportional representation.

This Jennifer Lawrence video summarises some desirable reforms: https://www.youtube.com/watch?v=TfQij4aQq1k

See also Lawrence Lessig's "Our democracy no longer represents the people. Here's how we fix it": https://www.youtube.com/watch?v=PJy8vTu66tE