The modern Santa Claus is derived from the European version of him,
which has more of a "Father Christmas" look about him.
They actually look pretty similar. The main differences are,
the European version is not quite as rotund,
his beard is not as wide or bushy, but still pretty full,
and his coat is much longer, down to his knees.
In Europe, this version is still seen much more widely than is the Coca-Cola version.