+1 alone does not mean the United States. Inspect the following area code and the NANP allocation records.
One shared plan
NANPA describes a plan covering 20 North American countries and territories under calling code +1.
The next three digits matter
The NPA area code is the first three digits of the ten-digit national number.
A location caveat remains
An area-code assignment is not a live location or a person identity.
Read the plan after +1
The +1 code identifies the shared NANP. The NPA is the next three digits; these symbols describe structure, not a diallable example.
Calling code
Symbolic structure: +1
Meaning: Shared NANP
Numbering-plan area
Symbolic structure: NPA / three digits
Meaning: Area or service assignment
Local part
Symbolic structure: Seven digits
Meaning: Central-office and line-number portion
The United States and Canada are participants, not the whole plan. A complete area assignment still does not locate the person or prove the current carrier.