Viewpoints: Is American politics broken?
The US government has begun a partial shutdown after the two houses of Congress failed to agree a new budget.
The Republican-led House of Representatives insisted on delaying President Barack Obama's healthcare reform - dubbed Obamacare - as a condition for passing a bill.
More than 800,000 federal employees face unpaid leave with no guarantee of back pay once the deadlock is over, as certain agencies and national parks also close.
Under the US presidential system, different branches of government can be controlled by opposing parties. Currently the Senate is controlled by the Democrats, while the Republicans control the House of Representatives.
This legislative conflict has led to the current gridlock and subsequent partial shutdown of government, the first for 17 years.
With the US political system seemingly in legislative paralysis, is American politics broken? Experts give their views below.
Darrell M West, vice president of Governance Studies at the Brookings Institution
The problem with American politics is that Tea Party activists have taken over the Republican Party.
They come from small, rural districts and now are demanding that House Speaker John Boehner practises extremist politics.
Boehner could end this stalemate today by allowing a continuing resolution to go to the floor for a vote without repealing Obamacare. It would pass and this crisis would be resolved.
However, conservatives have warned that if Mr Boehner allows a floor vote without their support, they will depose him and elect another Speaker.
This crisis is not so much a governability problem as a war within the Republican Party. It won't be resolved until prominent Republicans demand that the House takes action.
Prof Iwan Morgan, head of US Programmes at the Institute of the Americas, University College London
"Broken" is a very strong word. In one way American politics is working exactly how the founding fathers intended when they created the separation of powers.
But they always assumed that at times of need, the "energy" of government would overcome the separation of government. They never anticipated that there would be this polarisation of politics.
We're now in a situation where the intentions of the founders are being overcome by the nature of the political parties and the lack of middle ground between them, so you could say American politics is broken.
I don't think it's irreparable but you now have to have a supermajority [60 out of 100] in the Senate [to pass legislation], and the Republicans showed in 2009-10 how the lack of 60 Democrats in the Senate could be exploited to tie up the work of the upper house.
I don't imagine the Democrats will lie down and play dead even were the Republicans to become the single party of government in 2016.
Angelia R Wilson, professor of politics at the University of Manchester
Charges that America is broken are a longstanding trope of the US Christian Right. Such charges harken back to a fictitious 1950s shared cultural values.
Employing this measure, changes of the last 60 years indicate that American is "broken". But that fictitious narrative fails to include those on the socio-economic margins eg women, African-Americans, Latinos, and LGBTs, who are now moving at pace into the mainstream.
For these benefactors of change, America is not broken - it is increasingly realising its potential as a representative democracy based on justice and equality.
Change has left those previously occupying places of privilege outraged.
With more states allowing same-sex marriage, the working class accessing affordable healthcare, immigration reform afoot and a black man in the White House, the Tea Party has had enough. This government shutdown is not the culmination of their outrage, it is only a beginning.
Chris Edwards, editor of the Cato Institute's website DownsizingGovernment.org
There's no doubt that the federal budget process is broken, and there is wide acceptance of that. The federal budget system doesn't work. Congress hasn't passed a regular budget in many years now, [instead] they've appropriated money based on continuing resolutions and other special procedures.
The instability caused by the Obamacare health law is because it was passed in 2010 on a wholly partisan basis. Not a single Republican voted for the law in either the House or the Senate.
In recent decades the most enduring federal legislation has been bipartisan. So I would blame President Obama for ramming through legislation that only his party supported.
The battle over Obamacare is unique and has been poisoned, initially by President Obama.
That said, it used to be that both parties had both liberal and conservatives. But over the last few decades the Republican Party has become more conservative and the Democratic Party has moved far to the left.
Prof Stefan Halper, director of American studies at the University of Cambridge
In the UK, where you have a parliamentary system, if the prime minister's party loses a floor vote in parliament you have to have a new election - it's a vote of no confidence.
In the US, we have a situation where the administration's proposed policies can be blockaded by a minority in either House of Congress - and that can bring the government to a standstill.
The unusual thing in this case is that this radical faction, the Tea Party, have chosen to use the national budget [and] are demanding that the healthcare programme be modified or abandoned in return for funding government.
It's a form of political extortion.
It is broadly unacceptable to the American people, and the Tea Party will be hurt by it.
The system is stretched, the system is challenged. But the system itself is not broken. Eventually public pressure will come to play on the Republicans and will force them to accept some compromise solution. Both sides must find a face-saving way through this conundrum.
The House Speaker, Mr Boehner, has chosen not to confront the radical minority in his party, but rather to accommodate them.
A stronger or more principled House leader would've said "enough is enough". But he hasn't done that. So another reason the system is not broken is because it is a personality in a critical position who is not doing his job properly.
Hans A von Spakovsky, manager of the Election Law Reform Initiative at the Heritage Foundation
I don't think the system is broken, the system works. The problem right now is that the two political parties, who are fairly evenly matched in political support across the country, are having a crucial argument about the direction of the country.
This is not unusual; there have been prior times in American history where there have been substantive and critical fights over different issues.
We have an out of control federal budget, we have a gigantic deficit, and we're having a critical debate over what to do about those problems.
I don't think there is a serious structural problem in the US political system, we've just come to a fork in the road about the direction that the country should move in. The system is handling it, we're just at loggerheads over what to do about it - in particular where we should go with the growth and size of the federal government.
John E Owens, professor of US government and politics at University of Westminster
The [shutdown] goes to the basic structural problem in the US constitution.
It's a separated system with separate institutions sharing in power, so that means that each of the major institutions of national government can exercise a veto against any decision they don't like - and that's exactly what's happening.
Historically compromise has usually been available. [But] now you have an extremist group in the Republican Party holding the system to ransom.
What you have seen over the last 20 years in Congress is a kind of procedural arms race, and this is the latest example of it - one party, and it's usually the Republicans, finding some procedural device, [and] attaching this rider to a resolution to throw a spanner in the works and stop the government working.
I wouldn't say it's at breaking point but we've seen an escalation of the use of veto points. The "arms race" has been escalating and the parties have become increasingly polarised.