I suspect that even if the resources were owned by US companies, they still wouldn't mine them, for exactly the same reason.

Yes but it's an actual "homeland security" issue that we don't own the resources in our own country that are critical for our future infrastructure/transportation needs (vs. the theater issues at the airport).

Being owned by canadians, an economy that is intimately tied and dependent to the fate of the US economy, speak the same language and are fairly friendly neighbours overall isn't that bad. And if the US really wanted to, they could pass some BS law to retake those land claims.

If the resources are here and shit hits the fan (I don't see that ever being the case with Canada, but hypothetically), we can just take them. It's not a homeland security issue.

If you don't own them personally, why do you care about the passport of the guy who does own them?

There are a lot of Canadian resources owned by American companies. Should we swap?

Lithium is an alkali metal, not a rare-earth element, so it's not such a good example.