I'm fairly sure that the maximum G-force values in both the ATSM (F2291-11) and Eurocode (I'm not sure of the name for the Eurocode standard, but it seems to be slightly less strict than the British Standard BS EN 13814:2004) standards is 6G at most (parallel to the spine and for a period of a second or less). There's a number of graphs in the standards that show what you can legally do, [strike]so I'll find those once I'm back on a PC if you're interested.[/strike]
These limits are also for people upwards of 48 inches, and any coasters intended for people under that height have to be checked by an expert before they can be ok-ed.
EDIT: Here we go -
"Eyes down" are the G forces pushing you
into the seat, all the other directions have lower limits, due to what your body can take.
There's a whole load more of the graphs taken straight from the ASTM standard
here.
EDIT 2: To answer your original question: Yeah, the country-wise location of a ride will govern the standards it needs to conform to (so, for example, a Maurer coaster that's being built in America would need to conform to American (ASTM) standards rather than the German (DIN) standard), so the maximum permissible G-forces of the ride will have to match up with the specification laid out in the standard.