If you want to see how weird it can get look at blightsight. Your consciousness can be blind but your body can still react to visual stimulus.

The “I” is not the brain, the “I” is a part of the brain, which cannot function properly without the rest of the brain. Just like the brain cannot properly function without the rest of the body, or a hypothetical simulated body.

So rather: the brain is not us, but we are a part the brain.

“We” don’t exist, or rather “we” don’t know what makes us “us”, except for what we do know. Consciousness isn’t fully understood.