Jesus Christ, unless you etch your own chips and build a computer from scratch, the answer is always "we don't know".
There might be a backdoor in the cpu you buy, or in the baseband, or in a driver, or in an open source component that you didn't audit, or in your compiler, or even in your USB stick. You always need to trust somebody.
I am sure apple cares about privacy from government, but they don't seem to care about privacy of their users from them.