Beg to differ.
The nation is founded on the Declaration of Independence, which proclaimed the determination of the colonies to become an independent nation.
The form of government of that nation is indeed founded on the Constitution.
Right. But please notice exactly what I said:
"The United States of America is founded on the Constitution, and on no other document."
That's the Union of the People(s) and the Government of the Union. "America" is the country.