UA might be focusing more on LHR which makes sense considering the current decline in the overall UK to USA market but to call them London Centric is a bit of a flippant statement. Although it's a shame that BHX will loose it's longstanding route to EWR United Airlines will consolidate their UK operations at LHR as well as operating from EDI and MAN covering the major UK markets.
To think that at one point or another United Airlines (Continental) had a very comprehensive network serving the whole of the UK regions.
In the same way that you describe United Airlines are Heathrow Centric the same could be said about American Airlines.