I have been saying for years that the US will never be free of the duopoly without proportional representation. Proportional representation rather than winner take all is the reason that other countries can have many parties. If 10% of the district are Pirates and 5% are Tea Party, then the government should reflect that.

Only... it's not to the advantage of the duopoly to implement something like that, so... entrenched party structure will always be the single choice allowed