The UK was an example of consolidation resulting in terrible quality and limited choice. The "CAMRA" (CAMpaign for Real Ale) group is a result of push-back against this, and has been very successful: http://www.camra.org.uk/key-events-in-camra-s-history

Distribution all the way down the chain was consolidated — i.e Pubs — and was only remedied through legislation: https://en.wikipedia.org/wiki/Guest_beer

The US is nowhere near the same setup, though, so it's doubtful it would end up quite as bad. For beer at least, every time there's a consolidation, there's an opportunity for a new player to enter the market they just left behind.