Earlier this month, Twitter CEO Dick Costolo said, “We have things rolling out this fall that I am over the moon about and can’t wait for people to see.” The week before, race car driver Scott Dixon said he was “over the moon” about winning the Firestone 600.
“Over the moon” is of course a metaphorical way of saying you’re happy and excited. The Oxford English Dictionary’s first citation is from 1936. It’s not unfamiliar to Americans, but it’s traditionally been more common in Britain, as this Google Ngram Viewer chart shows:
In recent years, it’s mainly been the province of British and Australian celebrities talking about being pregnant or having a child, or athletes talking about winning a game. Such uses still yield the majority of Google News hits, such as Perth Now’s that an Australian businessman’s girlfriend has a baby bump: “’I’m over the moon. It’s the most wonderful thing that’s ever happened to me,’ the proud expectant dad told us exclusively.'”
But the Costolo and Dixon quotes suggest that “over the moon” will follow the lead of “at the end of the day” (which I see to my horror that I’ve never done an entry on) and become established in the U.S.
notoneoffbritishisms.com 
This is, or was, a popular expression with football (soccer) managers in post-match after a successful game.
Their reaction to losing was “I’m as sick as a parrot”! At one point I suspected they were quoting a “Manual For Managers” issued by the English F.A.
The Phrase Finder mentions “sick as a parrot” and other football cliches and Colemanballs being popularised in satirical magazine Private Eye in the 70s and 80s. It references the nursery rhyme about the lunar return-orbit cow, and says one of the earliest allusions to the phrase in print is “Charles Molloy’s The Coquet, or, The English Chevalier, 1718: ‘Tis he! I know him now: I shall jump over the Moon for Joy!'”
Hey diddle diddle,
The cat and the fiddle,
The cow jumped over the moon.
The little dog laughed,
To see such sport,
And the dish ran away with the spoon.
Oh, I missed narmitaj’s mention of this above.
Scott Dixon is a New Zealander, so unless he is a linguistic role model to the Indycar community, his use of the term may not indicate American adoption of the term.