If it was so fucking easy to discover shit why did it take Snowden to tell us all the shady shit the government is doing and all the companies they're in bed with that allowed them to do it?
This is a "why we still got monkeys?"-level line of reasoning.
One of those involves companies directly handing user data over to the government, under court order. In order to find out the truth, you'd need to be one of the few insiders involved in the agreements, and then break the law by leaking information about it. There's no way to detect that as an end-user.
The other is detecting network activity on a personal device which can be fully isolated and analyzed without interference.