In American election years, the electoral system that picks our next president tends to get the most attention. However, sometimes the very federal system of government operated by the United States also seems to get some attention. Specifically, every year a few individuals tend to call for the United States to move away from a federal system of government and towards a parliamentary one.
The arguments are based primarily from observations of other countries: almost all other nations on the planet use some form of parliamentary system for their government, and it seems to be working relatively well. Furthermore, a parliament would allow more third parties to be represented, and would reduce legislative deadlock.
But in the American system of lobbying, a parliamentary government would be deadly. It would firmly entrench special interests all the time and would destroy any semblance of political independence of many government organizations. Hence, it is easy to answer this question: the United States must retain its federal form of government instead of switching to a parliamentary one.