My fancy new Science of Cheese book (2014, highly reccomended [It's like all the helpful advice and knowledge from the forum in one book]) says that in 2011, the US exported 494 million pounds and imported 313 million pounds. It has a little chart, with which countries export which types of cheeses to US, as follows
Blue mold: Denmark, Germany, France
Cheddar: United Kingdom, New Zealand, Australia, Ireland
Edam and Gouda: Netherlands
Gruyère: Netherlands, Germany, Switzerland
Italian type: Argentina, Italy
Swiss and Emmentaler: Finland, Norway, France, Switzerland
All others: France, Denmark, Ireland, Netherlands, Italy.