People are acting like I'm making outlandish claims, you can literally just google this! If you are going to go down a rabbit hole I recommend USASpending, which consumes ATOM from FPDS and so is very close to source-of-truth.
Skimming OiG audit reports, they appear comprehensive and detailed. How has the government failed in auditing if these audits exist?
Where is the 20 years of failure to audit and track spending you mentioned? I’m not sure what you expect me to google.
You could maybe instead say that they should be under the same roof, rather than being independent entities. But I don't think this is itself evidence that any of them have been ineffective. Having read some of their reports, OMB and CBO are not ineffective on face value.
(I also don't think any of this is really about curbing government spending.)