Churning in Canada is more limited and Amex is pretty much the only serious game up here, I participate in it and have gone on many trips I could not have afforded to in J or F.
I have consistently kept my Amex Platinum over the years, even if it reduces the yearly MR I can churn significantly, because Amex has always been there for me from a customer service standpoint and the annual fee has been recovered many times from various insurance claims over the years.
I usually only need to send one message/make one call to Amex, the frontline CS reps seem more empowered than other companies. Sure seems that way at least.