[big-green-man]

The US government is modeled after Cromwell's parliament, almost exactly. The prominent difference is that instead of lords there are senators elected by states. The design has existed for a very, very long time, and evolved organically in England during and after the civil war. It might not seem like it is a good idea, but the US has been wildly successful. The design works.

There are a lot of powers the president has now that the office didn't have a long time ago, and the power of the executive has steadily creeped into everything and grown significantly. If the president were limited only to his powers articulated in the constitution it would be less consequential who the president was. Really, what makes it such a big change is all the executive departments that have regulatory and therefore de facto legislative authority.