So you think a citizen of France, while in the U.S., is no longer under the authority of France? Wrong. We’re not talking about criminal codes here. We’re talking about sovereignty issues.
No we aren't. We're talking about "jurisdiction". Not sure what you even mean about "sovereignty" because France has none of that either within our borders.
jurisdiction: "the limits or territory within which authority may be exercised"
A citizen of France visiting this country is subject to our laws and is within our jurisdiction. A diplomat from France is not.