One of this things you will notice as a Canadian or North American when coming to the the UK is that the variety of style was never concentrated as greatly as it was in North America. This could be down to any number of things.
The UK has tied house laws unlike those in Canada where independent pubs abound. In the UK Pubs are often owned by breweries and leased back to operators who are forced to supply only that brewery’s beers. Thus rather than putting their weight behind a single brand or few like Molson or Anheiser-Busch (if i misspelled there I’m not particularly fussed) the breweries were forced to attempt to appeal to all who walked through that pub’s door.
Historically we might also consider that when people colonized North America there existed no brewing tradition in aboriginal culture. When brewers did come to North America its not a stretch to expect that consumers were happy to take what they could get and brewers having much less resources than they would have in Europe were simply unable to brew a wide variety. Following this the large amount of German immigrants to the US definitely played a part in creating a brewing culture in many ways paralleling their own in Germany where in many regions the Lager or Pilsner was King.
Another cause for the endearing variety of style relative to North America would be the endearing traditionalism and lack of prohibition in The UK. Whereas the North Americans were subject to prohibition which killed small breweries and lead to a concentration of styles and breweries the UK was simply not. Regional beers and style were able to continue to be produced unabated and breweries were free to attempt a regional style to gain Market Share.
The greater consequence of this variety of brewing is less of a market backlash against the macro’s, as the macros to some degree have never stopped producing decent beers. I would take a british Macro Ale over a Canadian or American 999/1000. Of course Craft beer has come to the UK too. The positive effect of the variety of macro beers available in the UK is that british Craft Brewers have had to better than some great brews to gain market share whereas their counterparts in N.A. have just had beat the fizzy yellow swill.