What this chart doesn't show is the creation of any financial institutions or the growth of players outside this oligopoly...
I can show by the same mechanism that the human race will die out within a generation by the simple expedient of ignoring those being born.
Blackrock is the first that comes to mind, I read recently that it is fighting against being classified as structurally important because that would get in the way of its business.
Then there are the big retailers who will be quite happy to soak up customers pissed at actions like BoA's debit card fee.
Also PayPal isn't a trivial thing any more and we see moves by Facebook to move into some sort of retail banking position.
A small research project of mine is also trying to work out quite why there are so many Quants at Google and in particualar what their interest in fixed income is... Amazon does financial services as well.
Investment banking is global, and the difference between Americans and absolutely everyone on the planet is that when we draw charts like this we include non-american firms, yes they do exist, honest.
So any decent chart ought to have included firms like HSBC (itself the result of mergers), Barclays and UBS each of which have a non trivial presence. France has banks, yes, really, so does Germany and there's this "China" place that people tell me is quite the thing these days, it has banks.
Look at this chart here
1 of the top ten global banks is American
3 of the top 20
Also, look at how we got into this mess, not one single bank screwed up...
At least not a whole bank, components of diversified institutions went cancerous, by merging firms you increase the probability that they go bad. Some of the firms that got badly mauled in effect paid billions to acquire the business black holes that dragged them into their event horizons.