In North America, the Standard Pressure Region exists at and above 18,000 feet ASL and all low-level airspace in Northern Domestic Airspace (NDA). The object is to always have the altimeter setting while in the altimeter setting region (more in a moment), so climbing out, one leaves the assigned altimeter setting until in the FL airspace. On descent as mentioned above, one sets the assigned altimeter setting prior to entering low level airspace.
In Canada, we also have a horizontal requirement for setting standard pressure on our altimeters, and that is in the low level airpsace in the NDA region. The same logic applies horizontally as well as vertically: crossing the border from Southern to Northern Domestic Airspace, one leaves the current altimeter setting until inside the NDA, then switching to 29.92". Going the other way, one sets the current altimeter setting prior to exiting the NDA.
One big difference here is being alert for low pressure situations (altimeter settings less than 29.92"). It can get you in a heap of trouble. It is not uncommon to see very low pressure in Canada's eastern arctic, less than 28.20" on occasion. That's a difference of about 1700' of true altitude, not to mention cold weather altimeter setting source problems. There are also a lot of big rocks (~8,000') in the east & northern arctic region.