just think about how bad it was last time. Republicans don't give a fuck what they do to the country
But they do. We got the fiscal cliff because saner Republicans realized what they were doing and needed a face-saving out. There were some pretty vague and back-loaded spending cuts involved, but mostly they got nothing, plus a whole lot of embarrassment recently in the course of fixing (part of) the problem they created.
Boehner's ability to take hostages was always coming from his inability to control his caucus*. He was never presenting himself in negotiations as willing to let the US hit the debt ceiling. But if he can make his caucus eat a
tax increase when push comes to shove, despite the fact that they've just voted down his much more conservative Plan B, he has no credibility when he comes to Obama and says "those nuts in my caucus are going to force the US to default unless you give them what they want".
*Or his unwillingness to allow an unwhipped vote. But, again, if he's willing to allow it for a tax increase, he's going to be willing to allow it for a debt ceiling increase, because he knows that actually hitting the debt ceiling would be disastrous. Plus his speakership is safe at that point.
Edit: And I think there's reason to be hopeful that the current fiasco is going to stick to Republicans for a while. People are going to be prepared to blame them for whatever extraordinary measures would have to be taken to deal with a failure to raise the debt ceiling.