Clay Risen rejects the idea of an American a parliamentary system:
[W]hile the two parties don’t guarantee complete coherence, they play a vital role in corralling various levels of opinion and forcing Congress toward consensus. Just imagine if the United States had a parliamentary system like Germany’s. We’d probably have a center-left and center-right party, greens, libertarians, and progressives, too; but we’d also have a Texas party, a farm-labor party, a right-wing-fundamentalist party, an America First partyin a large heterogeneous society, the possibilities are endless. We’d be Italy, or India. There’s no end to the shortcoming of the Republican-Democrat duopoly, but it’s more effective than the alternative.