After Dubya Dubya two, Japanese industry wasn't doing so good. Among the smashed and bombed steel refineries and materiel factories were the devastated guts of just about every other industry, including the bering biz.
As the breweries of Japan began their reconstruction process, many American consultant companies, such as Anheuser-Busch, offered assistance. In some cases, the American breweries bought stakes in the fledgling Japanese concerns.
That's why Asahi tastes so much like Budweiser. Rice, rice, and more rice lend it a clean, crisp, disturbingly neutral character, allowing it to go very well with delicate foods like sushi, but preventing the beer from ever being considered particularly good.