A state is also a threat to its citizens. It's power must be limited through careful checks and balances. These create intentional inefficiencies. Combining the internal policing function with external espionage creates an organisation wilding the state monopoly on violence against its own citizens and able to claim it's actions are state secrets. Go ask how those released after years of imprisonment and torture in Guantanamo Bay without access to anything but a cruel mockery of due process how they feel about unchecked state power? Would prefer to talk to Uyghurs who managed escape from China instead?
The state must be kept limited in all its powers even in its power to protect from harm. Accepting the consequences of these intentional limitations is a price a society must pay for liberty or face the consequences.
In my opinion the USA has repeatedly fallen short in this regard. Coming back to your question here is an example of harm caused by (one-sided) information sharing: https://en.wikipedia.org/wiki/Parallel_construction .
The state must be kept limited in all its powers even in its power to protect from harm. Accepting the consequences of these intentional limitations is a price a society must pay for liberty or face the consequences.
In my opinion the USA has repeatedly fallen short in this regard. Coming back to your question here is an example of harm caused by (one-sided) information sharing: https://en.wikipedia.org/wiki/Parallel_construction .