American beers that are made with over 50% adjuncts are produced with American six row barley, which is a diastatic monster, but that's why they started doing it back in the 19th Century. At the time that the likes of Bud got going, mass produced glassware was only just becoming available to the public and the American malts were producing persistent hazes unless mashed with lots of adjunct.
There is a common misconception that American beers were full, rich and malty before Prohibition and that the use of adjuncts was a rort introduced by the few big surviving breweries after Prohibition ended. However, whilst hop rates have declined, their beers were adjunct laden from way back:
Encyclopaedia Britannica, 1911
In America the common system of brewing is one of infusion mashing combined with bottom fermentation. The method of mashing, however, though on infusion lines, differs appreciably from the English process. A very low initial heatabout 100 F. at which the mash remains for about an hour, is employed. After this the temperature is rapidly raised to 153-156 F. by running in the boiling "cooker mash," i.e. raw grain wort from the converter. After a period the temperature is gradually increased to about 165 F. The very low initial heat, and the employment of relatively large quantities of readily transformable malt adjuncts, enable the American brewer to make use of a class of malt which would be considered quite unfit for brewing in an English brewery. The system of fermentation is very similar to the continental "lager" system, and the beer obtained bears some resemblance to the German product. To the English palate it is somewhat flavourless, but it is always retailed in exceedingly brilliant condition and at a proper temperature. There can be little doubt that every nation evolves a type of beer most suited to its climate and the temperament of the people, and in this respect the modern American beer is no exception. In regard to plant and mechanical arrangements generally, the modern American breweries may serve as an object-lesson to the European brewer, although there are certainly a number of breweries in the United Kingdom which need not fear comparison with the best American plants.
