Seriously, there is nothing to apologize about. I've been in the USA for more than a decade now and it always amuses me when a subtle cultural difference pops up. On one of my trips back in the 90's I was at a breakfast restaurant in Boulder Colorado with friends and fancied an omelet - I asked the young waitress "do you do mushrooms" and without a blink she replied "occasionally" we all got a laugh out of that one.