Perhaps because of the milder winters, Europe and Australia were the first to heavily wear the jacket outside of the U.S. military. By chance, when MA-1 manufacturers began shifting from exclusive military contracts to civilian production in the late '60s through the early '80s, a variety of subcultures rose up throughout Europe, the U.S., and Japan.
English punks and skinheads would wear the bomber jacket over tucked in T-shirts, cuffed skinny denim, Doc Martens shoes, and other military-inspired gear like M-65 jackets and M-51 fishtail parkas. However, unlike the midnight blue and sage green you'd see on a military issue MA-1, punks often gravitated to jackets dyed in burgundy—something that would never have been released for military use, and was distinctly different from the jackets that came before it.
In Japan, as the cry for Americana in the '60s was it's own counterculture movement, there was an increased interest for American clothing imports in the men's clothing market. While this is traditionally associated with the preppy styles meticulously documented in tomes like Take Ivy, this also applied to American military gear. Japanese guys adopted both the MA-1 and the earlier B-15 as outerwear in the '60s and '70s, wearing it in a much more traditional way, styling it like servicemen in the late '50s or early '60s.