Hi Alea
Hopefully the Republicans will only have that majority until 2012. They aren't really the problem. The problem that lies at the root of this issue is that people know very little about economics in this country (apparently) and are willing to follow whichever pundit sounds most convincing-and unfortunately there have been several successful pundits that have advocated austerity for quite some time.
Any political strategy in this country focuses on the 1/3 principle. A third of people are solid Republicans, another third are Democrats, and the last third are independents. In order to win an election, either your party must have a much larger turnout on election day than the other thirds, or you must convince the independents that your program is better than the other guys.
I dont think the Republicans are as willing as you seem to think to let us default. There are too many interests on Wall Street that will take massive losses if a default happens. Instead, what I think you are going to see is a potential split of the Tea Party from the mainstream Republicans. Once the Tea Partiers see that the Republicans aren't willing to cause a default, they will begin to fragment away, which is exactly what Boehner and the real establishment is afraid of.
Meanwhile, the only thing protecting us from the austerity fools is our constitution, which spreads power out over three branches precisely for situations like this. When wackos get control of one branch, they must still get the other branches in order to do their damage.