The earliest tests done on residual samples from the Red Cross date back to December 13th and they show a small but significant positive caseload at that time. To my knowledge no other testing was done on earlier samples so in theory it could have been present before that in the US.
I’m in the US and I pronounce it, I think a lot of people do? Maybe I just know a lot of snobs and “regular” Americans mush the word together but I don’t think so