As an American, I see words such as cheerio, blimey, bloody (when referring to something negative), loo, bugger, fag (cigarette), etc. as chiefly British (I suppose they are).
What words and/or phrases do you consider to be chiefly American? I'm honestly unaware of which words I use that may not be used in other English-speaking countries. What other things in U.S. culture do you consider to be chiefly 'American'?