Language is a doable barrier to overcome, and so is harmonizing various regions on a regulation level. Remember that in Europe those cultural differences exist
within countries and have for centuries. Hell, Brussels itself symbolize that.
If you think they don't easily move from country to country, I suggest you visit London, Amsterdam or Berlin.
Harmonization is a political issue, and what hampers it is selfish and corrupt politicians.
Making it a cultural issue is dangerous nonsense. An average Greek would be quite happy to live under German style regulations, if he could trusts the authorities to play by the rules. Ordinary people and their cultural differences are not the problem.