The problem isn't getting to the US, it's coming home after my trip. After withdrawing my application (which would take the UKBA 20 business days just to return my passport anyway), I would have to reapply and pay another $900. The immigration rules changed just after I sent in my application, so if I were to reapply, it would be under different, less favorable circumstances.
Ticket details say:
Other Restrictions: NONREF/NO CHGES PERMITTED/NONENDO
I specifically asked if I could cancel and get a credit, and the agent said no; "either you fly those days or you lose your money."
At the end of the call, she had the gall to offer me hotel and car hire services for my trip!