- Human intelligence assets would be executed, as you mention. Witness protection program participants, too.
- Signals intelligence targets would stop using (or feed false information to) compromised systems.
- Consequently, the government would lose what little understanding it has of what's going on in the world, threats, likely outcomes of foreign policy, etc.
- It would also be incapable of any sort of undercover/sting operation, because every target of an investigation knows they are the target of an investigation.
- Diplomats can no longer talk about 3rd parties behind their back. No more conspiracies between allies to keep another nation (i.e. North Korea) in check. No more back channels.
- Diplomats must negotiate with foreign leaders in full view of their populations and political opponents. No more reasoning with leaders, brokering secret face-saving solutions. (Giving foreign nations an opportunity to back down without appearing weak is a staple of diplomacy).
- The budget required to replicate our military technology (including nuclear arsenal) shrinks dramatically, amplifying threats currently below the threshold of "serious."
- The nature of our defenses and locations of troops, installations, ships, etc. becomes public, lowering the bar to a successful attack.
- Some of the government's secrets are your secrets too. The full name/DOB/SSN mapping used to authenticate yourself to financial services. Home and family addresses for federal employees like prison guards, judges, and prosecutors.
- We've blown confidentiality, but some systems are not read-only. Properties like integrity, authorization, etc. often depend on the confidentiality of passwords and private keys. When the admin passwords enter public record, we have to assume all government databases and infrastructure (taxation, payroll, Exchange servers, PBXes for federal offices, etc) are promptly trashed by bored teenagers (or even better, overwritten with subtly wrong data/configuration for the lulz). How long before the email password of the Secretary of Defense is used to announce a foreign policy change? How long do you think the signing keys for a valid nuclear launch order will sit on Wikileaks before someone uses them?
- Do we count the federal reserve? Authentication factors needed to make arbitrary bank transfers are out in the open too.