whats the debate? America has a long and great history of brewing beer. From the Mayflower to today. Even 13 years of prohibition could not kill brewing in America, (although it did destroy thousands of small breweries across the states and forbade the millions of homebrewers from making thier own, and resulted in the domination of lagers in the US). Many universities tuitions (Harvard, Princeton) were payable in malt, and British brewers were using American hops as early as 1860s (Bass reportably got as much as 50% of its hops from Germany and California in 1869)
Sierra Nevada, Dogfish Head, Stone, Brooklyn, Anchor, the list of great American microbrews is huge.
So what exactly is the problem? I hear people say things like all American ales are too hoppy, or too strong, or in generall not as balanced as thier British counterparts and this can be said of certain styles but thats what makes them unique. By definition an American IPA is bigger and more bitter than an English IPA, but that doesn't mean all IPAs made in the US are this style, you can find a British style IPA in America, or a German-style Alt, or a Belgian style, or nearly any style.
I think people that dismiss American beer are just not looking hard enough to find the good ones.
