You mentioned two common generalizations, and not surprisingly neither of them reflects current reality. Scandinavians are not "just" strenght any more than South Americans are "just" flair and skill (another nearsighted generalization that is often repeated).
And while some english teams do insist on outdated methods, it's hardly a dominant trend anymore; today we see EPL teams with different tactical styles, some relying on speed and short passes, some others relying on build-up play and ball possession... so we can't say kick'n'rush defines english football anymore.
About the "merging" thing... well, the football world is more integrated nowadays, with the best leagues and tournaments being broadcast around the globe. And any tactical variation can be readily identified on spreadsheets or media-player files and forwarded to a hundred people... an intensive exchange of information that has allowed professionals worldwide to improve their methods and develop their techniques.
In the past WC that trend was noticeable, with previously-unsuccessful nations like Turkey, Senegal and others showning great improvement, benefitting from the "internationalization" of the game. Today, even Jamaica's players have experience in the top leagues, and that reflects on their national-level football.
However, I don't know about the "merging" of styles because there are core values that differ from one nation to another. A Brasilian fans' expectations and demands for his team are different from what an Italian fan expects... and a German fan will probably have his own ideas about how a team should play. World football is becoming more and more 'globalized', yes... and in a way that does benefit everybody. But different fans like different "flavors" in their football... and that's where the "globalization" will stop.
If a manager were to build a Brasilian team's tactics on the mold used in Italy, he might even collect good results. But sooner or later, outraged fans would be throwing stones at him on the streets and calling him 'retranqueiro'... because some values are not universal.
I think generelisations still exist, British and Scandinavian sides are similar in style of play, play with a high tempo, little technique or skill involved, as well as the germans. More grit and determination with them being very phyiscal. I see England as a side who defend and to try and play on the counter like they did at the World Cup with long balls. Okay it has improved but English defenders still aren't as comfortable on the ball as most mainland european defenders, besides maybe Ferdinand and perhaps Ashley Cole.
Okay most sides have moved away from their stereotypical styles to a certain extent but those styles still exist and no one can convince me they don't.
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