Did the terminal ask for a signature?
In practice it can get confusing, since both the card and the terminal have protocols that are not apparent to the user.
What you likely have is a PIN capable credit card, but other protocols (Cardholder Verification Method or CVM) with a higher priority than PIN. These CVM can be Signature, Online PIN, Offline PIN, No Verification as the most common. Both your card has a list of these, and the terminal has a list, the one that appears higher first on both is the method used.
Very few cards in the US have PIN as top priority as do very few terminals, in Europe Both cards and terminals have PIN as priority. So likely in the US, you will rarely be asked for a PIN, even traveling in Europe it will be a mix, with you being asked for a signature much of the time. The good news is that it should work in most unattended kiosks (for tickets, gas, etc.)
As for your experience at the grocery store, if you did not have to sign, then the "No Verification" CVM took over, which usually applies to purchases under a set Dollar amount, usually $25 or $50 depending on the store.