It's the same problem in the UK, big multinational brewers who produce general purpose beer, brand it and market the hell out of it, dominate. They get all the attention and "mind-share", and have all the sales and field teams to make sure their product is in pubs up and down the land.
There are smaller breweries here and in the US, the craft and artisanal brewers, and they make fine beers. They just aren't well-known. Also worth a shout out are the micro breweries, where enthusiasts can produce their own batches, both here and in the US. I can't speak for the US, but if UK governments past and present didn't think things like Appellation d'Origine Contrôlée were silly European ideas, our artisanal food and beverage producers would be a lot more visible.
The German law to which you refer is called the Reinheitsgebot
and there is a page on Wikipedia about it. Before I get completely OT, there are a few free software projects for the home brewer. I dabbled with QBrew
a few years ago, but haven't used it recently.