Well, you managed to completely miss the point.
Maybe that's because there wasn't one. Or because you explained it badly.
Country A is failing fast. Country B is not doing so hot, but far from failing just yet. Countries, in their death throes, typically inflate the shit out of their currency, to try and prop up their economies. This means that,
ceteris paribus, A would have a much higher inflation rate than B. Putting them on the same currency C forces A and B to have the same inflation rate. Two things could happen here: C slows A down to the inflation rate of B, or C speeds B up to match the rate of A. If Bitcoin (or any hard currency) were C, the former would happen. They'd have no choice. But since the Euro is fiat just like every other type of funny money out there, the latter happens, and B's economy is dragged down by A. A good look at the last decade shows this clearly.
Instead of putting the brakes on the collapse of European economies, they poured on the gas, and ensured that everybody hits bottom in quick succession.