The US has many beers and ales that are as good or better than the best from the UK.
While I don't really like beers like Budweiser, it's actually a very high quality product. It's truly amazing that they're able to produce such large quantities of lager and keep it to such a high standard.
What I don't like about Bud is the style. Luckily, there are many other styles of beer and ale made in the US. Even A-B can produce a great beer when they choose another style.
I suspect that there are a wider selection of styles produced domestically in the US than are produced in the UK, and we have a larger number of good beers and ales. (We're a larger country, so it's no surprise.)
I also greatly admire many of the beers and ales produced in the UK. (And in Belgium, Germany, etc.) Who has the best beer is a rather silly thing to be arguing about, don't you think?