It doesn't work like that. If the US and Canada stopped extraction of oil and gas for the most part that shortage would be made up in other places. As we remove our supply from the markets prices would rocket up and countries like Russia and Saudi would make immense profits while making up for most of the losses and not moving the demand needle as far as you think it will move for the environment. There will also be a move back to coal where that's an option (some power stations).

And that's ignoring the consequences of that on e.g. people in cold climates that rely on gas for heating or people that rely on gasoline for getting to work. The correct approach is to reduce the usage of fossil fuels which will lead to reduced extraction naturally.

You're not 100% wrong but the impact is marginal. Partly because some energy markets are a cartel. The prices aren't strictly governed by supply and demand but rather supplies are throttled to drive prices.

This is why that's the wrong thing to focus on. If we (e.g. Canada and the US) have strong economies that allows us to do more. Both internally and by influencing others. For example I can afford to drive an EV and use a heat pump because the Canadian economy does well, despite those not being economical options. Many early adopters of solar and EVs and other environmental approaches were only possible because we have strong economies, and those drive down prices for everyone.