Earlier quoted context omitted.
The WAMU bankruptcy was difficult for the FDIC to manage, and there was no ready buyer to take the remains. But if there had been no FDIC to manage it, the result would have been catastrophic failure. Like Lehman, but with more retail banking customers getting wiped out.
Congress would have given the FDIC a blank check if they needed.
Congress already did this. The FDIC reserve fund is mostly an accounting and accountability thing. The act creating the FDIC gives it the explicit backing of the United States’ “full faith and credit.”