Why has this kind of governmental crisis been allowed to go on so long? Is it just partisanship taken to extremes on both sides?
Its allowed to go on because the US consitution doesn't really allow you to do otherwise. The consitution basicaly assumes that it will be possible to obtain broad agreement on any important matter. This hasn't been the case for quite a while but a series of kludges has kept things going. These do however require that there are a significant number of people on all sides who behave. This is no longer the case. There are various reasons for this. Not least of which is that politicians are now more in touch with voters who don't like compromise deals conducted behind closed doors. The republicans in particular are aware that their supporters want them to act in ways that will break the system.
In fairness this isn't unique to the US system. Most systems require a fair bit of people following unwritten rules. The 1975 Australian constitutional crisis and the recent difficultly in forming a budget in Belgium being two obvious cases.
The US is though at a particular dissadvantage. The 1975 Australian constitutional crisis could be resolved by an outside agency and the Belgium thing appears to have been mostly a single issue disspute which allowed a caretaker goverment to get on with running the country.
To consider the UK case. Probably the closest equiverlent is that you can in theory fillibuster a bill in the house of lords although convention says you shouldn't. Labour tried this recently with the AV bill.
There are a number of problems with this:
1)It has to be a real fillibuster
2)The house of lords is full of people whith nothing better to do than disscuss word etymologies at 3am
3)the bar doesn't close
4)as long as the goverment has a reasonable majority in the house of commons (and they almost always do) they can use the parliment act to force the bill through or just flat out abolish the house of lords.
So the US has things worse because stalling is less problematical and there is no overide option.