When options are slim, what gives the most impact?

For context, I'm going to need to buy cereal at some point (even though I prefer oats), but this applies to anything, really.

So many of these "buy Canadian" websites will list companies like Post and Kellogg's, because they have manufacturing here.

But there are also Canadian-owned companies. Some "have manufacturing in Canada or the US", and there's no guarantee that the ingredients used are even from Canada.

So... when there are no Canadian companies who make products in Canada, which alternative gives the most impact (i.e. keeps more money within Canada)?

Is it better to buy products that are made in Canada, even if the company is American owned.

Or should priority be on Canadian companies, regardless of where products are made?*

*I'm totally fine supporting products made outside of the country, if I have to. But American made is at the bottom of my list.

For my wife and I, I could likely make our own mix of muesli cereal from Canadian and NotAmerican ingredients. But our grandkids are used to regular cereal brands, so we need to accommodate.

What have you guys been doing?