Is the brain mentioned in the Constitution?
No, but the concept of the brain is presumed throughout. The Constitution is thus founded on the concept of the brain.
And the Constitution is founded even more directly on the concept of God, via the principle of rights.
Your brain analogy is silly and will be ignored.
The influences on the bill of rights were from many different places, both secular and religious. The concept of human rights and rule of law goes back thousands of years and hundreds of years before Paul wrote his version.
The US didn’t perfect human rights in their founding documents either, as it made allowances for slavery is one example.
The constitution explicitly states there is no national religion. The type of Christianity practiced by most people who claim the constitution is their work didn’t even exist then.
It is not yours or your version of Christianity to claim. It gives you the freedom to worship as you choose, but no special right to enforce it on others or claim ownership.