What is the symbolism inferred by charlemage's crowning as holy roman emperor?

I don't know the symbolism behind Charlemangne being crowned an Emperor of the Holy Roman Empire . What I have read, though, is that ther is evidence that 34 of our 43 presidents have direct lineage to this Charlemagne (742-814). U.S. has been compared to Rome as the Gobal Super Power that we know it is... For more look into David Icke.