Pretty much the same. Europe uses research octane (the R in R+M/2) which typically gives several points higher than the motor methode (the M) of determining octane. Due to additives and such, there is no exact conversion, as one factor may skew one methode of octane determination more than the other....and that is the claimed advantage of the R+M/2 measure. It is harder to game the testing to get a better number to advertise. (like the chinese did with the animal food) The "M" part pretty much nails down the anti-knock property of the gasoline.
If it is not specialized racing equipment and not carboned up, it will be OK on american premium pump gas.