As an aside, For all those who talk about corruption and getting money out of politics I suggest reading Federalist 10 by Madison. Its a deep analysis of a need for a republican democracy. Any government that depends on human virtuousness will fail. The only way to have a sustainable government is to have strong checks and balances and putting multiple factions with different interests against one another.
I don't think this viewpoint can be supported empirically. The US government has much stronger checks and balances than most parliamentary systems where the prime minister is elected by the parliament. This means that there's no split possible between the executive and legislative branch. I think the result of this in the US is that the government tends to deadlock, and has a lot of difficulty compromising, which leads to dissatisfaction and instability. Conflicts heighten without compromise or resolution for decades until they reach a breaking point. In a parliamentary system, the need to build a governing coalition can result in greater incentives to compromise.
Similarly, judicial review seems to be much much weaker in most countries. In the US, the supreme court can strike down a law with immediate effect of nullifying that law. It's been hard for me to find comparisons, but it seems like in other countries, there's some combination of judicial review being only advisory, or not having immediate effect. So in some countries, the judicial branch says a law is un-constitutional, and the legislative branch can ignore it, or has some period of time to defend or revise the law, rather than the law being immediately struck. This is fundamentally undemocratic. That's a good thing some times, but not good other times.
In practice, parties tend to govern by attempting to control the supreme court, because there's no possible way to pass their agendas due to our vaunted checks and balances. This does not seem like the hallmark of an effective democracy to me.