In the Irish political system, we have a government which exercises all executive and legislative control. When we elect them, we're basically handing to them the power to do what they want for as long as they're in power which can last for up to 5 years. We also have a president whose powers are far more limited.
It might not be perfect but it means that when the people vote a party or parties into power, those party/parties receive a genuine mandate to effect change.
In the US system, the president has far more powers including the power to veto a bill. The Senate and House of Representatives can also shoot down proposals from the president. Once upon a time, both houses were almost always controlled by the same party that controlled the White House. Between the start of the 20th century and the end of Lyndon Johnson's reign, one party or the other controlled the whole federal government -- the White House and both houses of Congress -- for 54 of 68 years, about 80 percent of the time. So there was little friction between the centres of power.
Since then, the USA has had one-party government for just 14 of 44 years, less than one-third of the time. These days, at any given time, the president is likely to be from one party whilst one or both Houses are controlled by the other party. As if this in itself wasn't enough to guarantee the sort of legislative deadock that we see over the fiscal cliff issue, consider the fact that congress is now more partisan than it used to be. Whether it's the environment, gay marriage or "Obamacare", Republicans and Democrats just have a lot less to agree on these days.
Like almost every developed country, the USA faces major fiscal and demographic challenges. Yet, its founding fathers seem to have bequeathed to 21st century Americans a system that puts far more emphasis on checks and balances than on taking critical decisions.
1. How the Congress Became More Partisan - Infographics
2. Eric Black: U.S. or Parliamentary System? One Is Nearly Gridlock-Proof -- and It Ain't Ours
3. Our role in America's political divide | StarTribune.com
4. The dysfunction that lies at the very heart of American politics | Michael A Cohen | Comment is free | The Observer