When I asked 4 months who was the bigger case maybe it wasn't as clear. However it is becoming clearer and clearer that Europe is by far the bigger basket case. Another important point: the US does not stand the same risk of Japanese stagnation.
The answer to the question of whether we will go the way of Japan is: no. And the answer to who is the bigger basket case is Europe.
The reason Europe is in such worse shape is twofold. The first reason is the monetary structure of the EU is a mess with no lender of last resort. This is what there is no debt crisis in the US, Britain, or Japan but only in the Euro countries.
However the second reason is also the reason we won't go the way of Japan. Unlike Japan or Europe we have these advantages: a growing population that is also highly heterogeneous. Then of course the US has the advantage it always has had since the start of this country of having such a big, vast country with so many national resources.
When you figure out what went wrong with Japan, part of it is the population is shrinking. During it's boom years of the 70s to the early 90s Japan had significant population growth. Since then they have been shrinking. In Europe anti immigration bigotry takes away the one way this dangerous population contraction could be reversed or at least mitigated.
Yet France that likes to fancy itself a "cradle of democracy" has taken the extreme step of discriminating against Muslim women.