About the only type of beef that is imported is cooked and/or canned, e.g., corned beef, etc. The U.S. is about the only country in the world who still can produce grain-fed beef at a low cost. I don't know of any country that exports grain-fed beef into the U.S. but if so, it would be very identifiable because of its high cost, i.e., Kobe beef.
Muleteam1
The live cow that tested positive for BSE last Christmas was imported from Canada.