The handy Australianism “no worries”—usually used in place of “you’re welcome”—has been burrowing deeper into the heart of American English.
According to the Corpus of Contemporary American English, a free, 450-million word trove assembled by Brigham Young University’s Mark Davies, the phrase has been popping up in stateside lingo with increasing regularity. Usage of the phrase rose to 1.5 per million words in 2011.