Not enough instant gratification in Soccer
That's my opinion as to why it doesn't really touch the American public the way Baseball, Football or Basketball does.
What amounts to a home run trot/game winning field goal/interception for a touchdown or a dunk is a goal - and that happens (on average) less than 2 times in 90 minutes ? a contest.
There's no pitching changes or time outs to slam commercials down your throat either, so it's certainly not as heavily promoted.
Kids in the states want to be the next Deion Sanders and dance in the end zone or dunk like Kobe and drink Sprite.
Robert, as far as the naming goes, MLB has been using the term "World Series" since 1903 - it was originated more to solve a dispute between the old National League and the American league. I like to think that the best players in the World play in it - the vast majority of which were born on this little island - so I find the name fitting.
As for my New England Patriots (season ticket holder since 1994) they are the World Champions and I'll hear nothing else on the subject thanks.
Go Red White and Blue (USA and Patriots!)