Make sure to post your questions to Products.
I wouldn't use Inferred Country a base for legal decisions, since it is known to be inaccurate. Merely venturing across the border on a business trip or using a US-based VPN doesn't exempt a lead from CASL. But your own legal team would be the ones to make that call.
On the flipside, if you use Inferred Country == Canada as a baseline to include leads under CASL restrictions, there's no legal harm in that (though you will erroneously include some leads). But that's a subset of the leads that actually need to be included.
Thank you Sanford! I will go ahead and not use it to be safe. I will also post my questions to products.