I doubt its a true difference, but merely playing with the stats a bit. I'm not sure, you'd have to look into where they are getting their numbers. If you look at the CFF (US) website, you'll see that the 37 is a "predicted median age". Which doesn't mean that patients are living to about 37, it means that they predict half will make it past 37. However, they recently reported that only about 47% are currently living past the age of 18. URGh -- stats can be confusing and different sources can use them for whichever purpose they wish to.
So are Canadian CF patients living longer than American CF patients? Possibly yes, but possibly no.