Sorry but there is no fix for that ever. No matter what you try, each individual agency is on their own Empire Building trip trying to get as big as possible so that they are impossible to destroy as they are too valuable or have their funding cut.
These same places will spend a Million $ to save a cent and boast about the savings that they have managed to achieve.
However the big thing here is that by design these places where kept separate as the people involved in starting them never wanted any one group to get so big that it was indispensable. Hence the agency investigating Foreign items is unable to talk to Domestic Investigators and the Aircraft Monitoring Authority is prevented from speaking to anyone not directly involved in Air Travel.
Some see it as stupid while others see it as a way to prevent any one agency getting so big that they control everything. The people who designed the system tried to prevent the latter and to that end have done a fairly good job of it.
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