Likely because the European spec equivalent of the U.S. Spec is not available or even made. It would be almost impossible to find the constant steady stock of U.S. spec oil in Europe so the auto manufacturers (in the U.S.) had to try some spec to see if it meets the engine requirements and came of with the Euro Spec of 0w40 which would meet the warranty needs.
that makes sense and maybe why the op sees different oil recommended in different countries. but yeah. interesting