Partisan politics in the US is too narrow, with constant exchange of power between two groups. In countries that have 3 parties to vie with and question each other, each party always has an opposition of two others. There are many people for whom one of the traditional parties is a poor fit, that are selected only on the basis of the broadest principles. The current parties are inadequate, with a religious association. If you are Christian with socially conscious leanings the Republican party may not be a fit. If you are a fiscally responsible Humanist, the Democrats may not be a fit. So any political party that opens up the landscape is a good thing.
While America needs a third party to balance out the political landscape, the need is not for a party with such radical convictions and such unwillingness to compromise on many crucial issues. The religious affiliation of the tea party is also a terrible thing for the country, and the modern world