Does by selecting "Chose your coverage: Canada+USA" implies that calling to Canada+US numbers is included in the plan if the subscriber is in either of the coverage area?
Well, the number you are calling must be a Canadian or US registered number.
So technically they can be anywhere in the world, you would still be able to call them no charge. In other words, it's not where they are, it's where the number is registered that is taken into account.
Also, as a caller, you can be anywhere in the Canada+US zone and benifit from rooming coverage at no extra cost. Meaning you can make or receive calls wihtin the Canada+US zone without extra cost.