Matt Yglesias writes:
As a general matter, I tend to think parliamentary systems as seen in Britain or Canada are superior to our method of government. A system like that puts less formal restraint on the head of government in terms of his ability to act, but also makes it much easier to dump a head of government whose policies have failed and whose leadership is widely considered inept.
Totally maybe. Parliamentary systems do work better for small countries with well-educated populations. Accountability is higher, and voters enforce some discipline upon government. The openness of the economy imposes other constraints. See this paper.
But when the country is large and diverse, I see more reason to favor the American Constitution or in general a more pluralistic system. Why trust voters as the major source of constraint, and what do "the voters" want in any case? Furthermore the American system offers a decent chance of divided government and thus greater limits on the executive. Parliamentary systems often allow the Prime Minister and cabinet to manipulate the legislature by offering intra-party perks and promotions. There is plenty of gerrymandering, and bringing down a government is an extreme option which is not very easy to exercise in political equilibrium. If nothing else the rebelling party faces the danger of many of its members — including the rebels — being kicked out in a new election. Elections can be called at strategic times, and so on. The Prime Minister is hardly a captive of the voters or the legislature.
Federalism is another issue. If so much of policy is decided in decentralized fashion, as it must be in a large nation, maybe the federal/national part of those policies should be decided on grounds in rough concordance with a federalistic system. That will mean a division of powers. I also worry that as the nation becomes big enough, and states matter more, that there is not enough party unity to sustain a Parliamentary system.
When the executive and legislature are unified, as under a Parliamentary system, the Supreme Court, or its equivalent, will be weaker. No one will trust a hand-picked court, with no major obstacles to confirmation, with so much power. Yet weakening judicial review in America would worry me; it also also one step toward eliminating a written constitution altogether.
A final question is whether the USA — the country most likely to use nuclear weapons — needs a President with a certain amount of autonomy and secrecy for a fixed time period. In general I favor a constrained executive, but that one is harder to call. Can you imagine a Parliament debating nuclear strategy?