Let me repost my last message, as it seems that it didn't work very well - at all and is completely unreadable. (I did it on a WebTV at a friends house and it certainly didn't come out right.)
Anyways, in response to your question, yes the answer is Delta. They serve more destinations in Europe at 23, while United serves, I believe, 18. Delta are the #1 airline from the US to Europe.
BUT the other way around, the answer is that no airline serves as many destinations in the US from Europe than British Airways.
Delta serves the most EU destinations from Atlanta, Cincinnati and JFK, and BA serves more US destinations NON-STOP from Europe to the US.
Sorry 'bout that.
FLY DELTA JETS and sail UNITED STATES LINES
N 8 6 3 D A