Cars 2 was the first Pixar Cars film to feature a major international spy plot. The sequel combines Lightning McQueen's World Grand Prix races with Mater's accidental involvement in espionage.
Mater is mistaken for an American spy and becomes entangled with secret agents Finn McMissile and Holley Shiftwell. Their investigation concerns a criminal scheme connected to the World Grand Prix and a supposedly revolutionary alternative fuel.
The film travels through Tokyo, Porto Corsa, and London, making its setting much broader than the primarily American locations of the first Cars movie. Its structure gives Mater and the spy characters substantial narrative focus.
Cars 3 returned to a more racing-centered story about McQueen's career. Cars Toons is a separate series of short films, so it is not the answer to the question about the feature-film franchise.