English was an accident. The formal language of the Hensedag was low German well into the eighteenth century. Anyway, I suppose that a different outcome in the imperial succession could have done it. The Hohenstaufen had a good chance of holding on after the death of Frederick I through sheer prestige. Without the efforts Henry VI Leo fostering the cities of the north and putting capital in the development of trade and industry, the influence of the urban upper classes might well have remained limited.
If you're going to say one POD, make it the 1162 Privilegium Macellorum et Geldorum. It became the pattern on which all Hanseatic (they call it Geldic or Gildic in High German. BTW, Hansa is a terrible anachronism they only use for history books) polities were based.