Saitama is living in MCU Japan when he's inspired by the Avengers' battles with monsters in New York (i.e. the first Avengers movie) to begin his legendary training regimen of running 10km a day plus 100 daily push-ups, sit-ups, and squats. Flash forward a few years, and he's reached the same power level, appearance, personality, etc. he has in One Punch Man. With most of the villain/monster activity in the MCU occurring places other than Japan he decides to travel the world and try to join the MCU equivalent of the hero association, the Avengers. What happens? Assume he emerges on the scene sometime between the Avengers and Infinity War, that he somehow ends up with the moniker of "Caped Baldy" and the same general apathetic/unimpressive demeanor, and that his power level relative to the setting is consistent with his power level in OPM--i.e. he is just as capable of one punching any being in the MCU as he is his own opponents in his series, up to and including Thanos. What changes, for both him and for the MCU?