In Canada, The United States, and Mexico, the advertised octane rating is the average of the RON and the MON, called the Anti-Knock Index (AKI). It is often written on pumps as (R+M)/2. AKI is also sometimes called PON (Pump Octane Number).

Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel.

There's a table in the wiki article that shows the equivalence of different systems

https://en.wikipedia.org/wiki/Octane_rating

Yes. USA, Canada and Mexico use a different rating. You need to add about 5 to get the same number on the more common RON scale.

There's two primary ways to measure octane. RON and MON. Most countries pick one- specifically RON. The US and Canada average the two, for some reason.