It would generally be considered null. Most interfacing between police departments is through Interpol, the FBI, or the State Department. There is almost no reason for a local cop to have any standing in a foreign country.

That said, for some strange reason, the New York Police Department has an intelligence arm that works in foreign countries and is coordinated at the city level. Because of that, it is possible that New York City has independent relationships with foreign countries that doesn’t go through the US State Department. This came up as former mayor Eric Adams was caught getting bribes by Turkish officials for leniency in permitting for its NYC embassy. So, it is possible that a NYPD cop could have more pull than the average American local cop because of these relationships.