Germany's mechanized forces drove a spearhead through Picardy to the English Channel today in Adolf Hitler's climactic blitzkrieg against the Allied armies in Northeastern France and Belgium. The Allied forces fought back grimly but apparently without seriously checking the Germanys and, in Paris, Premier Paul Reynaud charged that "unbelievable faults" had been committed through failure to blow up a bridge over which the Germans first smashed through the Maginot line defenses on the Meuse river.