I agree with Eichengreen that the EU's inability to grow is a huge political risk. And it is a global risk, given the deep historical linkedness of west European societies to the rest-of-the-world.
The trouble is, setting Europe on a course of economic growth may not be possible. As historical evidence indicates, a chronic inability to grow has been the EU's curse throughout its existence. Managing the problems of geopolitical power arising from this chronic size-impairment is, as I have documented in my book, in fact the main rationale for the EU's creation. It is this chronic inability to grow beyond a certain global share that the EU's repeated enlargements were designed to mask, and they did so with remarkable effectiveness--until recently.
However, masking is not the same as fixing. Enlargements only swept historical structural issues under the rug. I have made this argument several times; last time using this graph:
In the graph, EU-enlargements appear as the upward-pointing "jumps" in the line representing the EU's share in gross world product. More important, we see a clear downward-sliding tendency during the years that did not involve enlargements.
A somewhat more puzzling question is why we talk so much about the EU's lack-of-growth nowadays. I can think of two, more or less simultaneous, reasons. First: The EU is pretty much running out of credible "accession" candidates, given the criteria for admission (having a particular kind of political system, predominance of a "European identity", whatever that means, etc.). This is especially the case for states the EU needs most--i.e., ones that are large enough to provide more resources--i.e., most important, cheap, qualified labor--for economic growth.
Second, all this is hitting the EU at a time when its longue-durée objets-de-désire and geopolitical nemeses--especially China, India and Russia-- (as well as such other, not-so-tiny societies as Vietnam, Indonesia and Brazil) are growing remarkably fast, much faster than 'Europe', wherever one might want to draw its boundaries, or even "the west" (e.g., see the direction of the line representing the US in the graph above). In other words, west European capital's (and, hence, by political extension, west European populations') shares in the global pie are slowly and, as far as I can see, unstoppably, shrinking. And along with those declining shares in global value added, we see the erosion of west European influence over the global system as a whole. (Hence, e.g., the psychosis about "China's meddling in Africa.") Part and parcel to all this is western Europe's growing economic dependence on these societies, not just for raw materials, energy and labor, as throughout the history of capitalism, but also for affordable finished products and services. These are the principal processes that create the current concerns--which are, hence, obviously about much more than small technical issues of "European growth" and domestic politics in the less-well-off European states.
The current discussion about "European growth" is, thus, about the character of the emerging, new global order in the most profound sense of the word.
There is of course a solution: a slow and resolute process of cultural change whereby European societies would gradually learn to live at less than 3 times the world average per capita GDP and not treat the rest of the world as their own private corporate playground. But that of course would require "soft power" and "civilization" on part of the European states and the European Union--the two things their political systems sadly lack, in spite of all the rhetoric to the contrary.