As previous posters have mentioned - no chip and PIN in the US yet (although just back from Australia and all Chip and PIN there).
One thing to watch in the USA is some retailers, once you swipe your card, automatically default the payment to your "local" currency. In my case GBP£ and it would seem at a much worse exchange rate than the one obtainable if using your credit card in USD$ and the cost being converted back to GBP£ by your card issuer on your statement. Watch the payment slip and becareful what you sign.