The Canadian battery does not have approx the same CCA. It has nearly 25% more. 450 vs 550 CCA.There are 3 major battery parameters that are important.
CGA is the amount of current that the battery, when charged, can supply at a given temperature while maintaining a given voltage.
Capacity is the amount of time the battery can last, on a given load (given current)
Deep Charge is if the Battery will survive repeated full discharges, without major deterioration.
It's possible to have a battery with a High CGA, but a low capacity.
It can provide the current (when fully charged) to start the car, but not for very long.
Example: Small Lithium emergency starting devices.
Then again, you can have a physically BIG battery, with lots of Capacity (last a long time), but can only provide a limited current when put on load.
With that being said, getting a PHYSICALLY bigger battery does not necessarily give you higher CGA - that depends more on the construction of the battery, but a Physically BIGGER e battery will typically give you more CAPACITY, so will allow you to listen to the radio with the engine NOT running for longer.
The question is, why do the Canadians get a Physically BIGGER battery, with approximately the same CGA as the smaller American battery ?
Either they need the Capacity because it takes longer to start the car in their colder climate .. or .. They need listen to the Radio a lot more with the engine not running. ?