Technically article title is incorrect and should be "...no US PASSENGER airlines operate the Boeing 747" -- UPS Airlines is US based and still operates the 747-400[1], it is just they are a cargo airline and not passenger.
One of the first things I noticed using FlightRadar24 and similar services is that there are a ton of 747s in US airspace used for cargo, many owned by relatively small firms.
1. https://en.wikipedia.org/wiki/UPS_Airlines#Fleet