I realize this is a question that might be viewed by some as beating a dead horse: "why do American beers taste so bad?" This has been commented on, talked about and asked a million times, especially with the growing popularity of craft beers, and I'm not trying to do that and pass a judgement on whatever people like to drink.
What I'm just really curious about is if there's just something illuminating historically on why beers that were started by German immigrants - Busch, Coors, Budweiser, Pabst, etc. - are so distinctly different from the rest of German beers as well as if they actually do taste different in comparison to beers through out history? Was this beer actually very similar to how German beers were at the time that immigrants brought this over? Was it just simply what caught on with Americans in general and it grew into what we have today? I know the internet frequently mentions prohibition. Did this spark something?
I'm really curious about the latter part of the question because, like mentioned earlier, it's frequently talked about how bad popular American beers are in contrast to the rest of the world, like they're some sort of outlier in the beer industry, but are they actually?
I'm not a historian of beer and brewing, but am a brewer with an interest in the history of the craft.
American adjunct lager (already described by u/Regalecus ) traces its history back to the mid-nineteenth century when immigrant brewers from Europe (particularly Germany) arrived in America and attempted to replicate the beers they'd brewed back in Europe. With limited success.
The key ingredient in beer is malted barley. Most American barley at the time was "six-row" barley, different from the "two-row" varieties common in Europe. The names describe the arrangement of the grains of barley around the stalk, but the key differences lie elsewhere. Notably, six-row barley is higher in protein than two-row, which makes for hazier beer, and makes some steps of the brewing process more difficult. Also, six-row barley has higher diastatic power than two-row, meaning that it is higher in the enzymes that convert starch into sugar during the mashing step of the brewing process. Corn and rice (called "adjunct grains" in brewing) are cheaper, weaker in flavour, lower in protein and have no diastatic power at all.
So the American six-row barley encouraged these immigrant brewers to substitute a portion of the malted barley in their recipes with adjunct grains to produce clearer, less expensive beers. AND, because of its higher diastatic power, six-row barley allowed them to do so. But in doing so, they also made their beers less flavoursome than those they'd brewed back home.
This is one part of the puzzle.
Aside from the technical reasons, there has been a general trend in American consumer preference towards lighter flavoured beers for decades. There are doubtless many reasons for this, but probably the biggest single one was prohibition. Beer, especially strongly flavoured beer, is something of an acquired taste. During prohibition a whole generation of drinkers came of age without having a chance to acquire it. When prohibition was repealed, strongly flavoured, bitter beers were just too much for the palates of consumers who had spent over a decade drinking soft drinks and brewers, naturally, catered to this market.
I'm sure there's more to say, and I'd be delighted to see what any actual brewing historians have to say on the subject, but hopefully this is a good start.