The CFAA is a federal statute. Activity that violates 18 U.S.C. ยง 1030(a)(2)(C) may occur entirely with the borders of state.
How can the federal government have jurisdiction over such an activity? The answer is that the federal government has jurisdiction if the activity affects interstate commerce,
The courts have held that any use of the Internet affects interstate commerce.
So the CFAA applies to any access to a computer.