Half the population in the US hates you then, to be precise. But the other half loves you. And having half the population in the US as your readers would be quiet a progress. People like Michael Moore seem to live quiet well this way. ;)
The "boring" thing is a valid point of course, not only are both side equally bad, but also their wrongdoings are repeated again and again, and a lot of writers/comedians ect. have already pointed that out already.
Nevertheless, Michael Moore still lives quiet well from it.

But seriously, you can criticise without taking one side. As you say, there are faults that all politicians have, and nobody can deny that. Look at Mark Twain, he criticised politics a lot - but not so much aiming at one Party, he rather pointed out the fundamental flaws in the system. Which makes it hard to disagree with him, even today in a totally different society.