For perspective: all EU states have freedom of movement for their citizens (meaning an national identity card is valid for crossing borders) like you can visit Germany as a Spaniard for instance up to 180 days (includes both Switzerland & Liechtenstein), applies to every country within the EEA. Permanent residency is guaranteed for EU citizens after 180 days given you must work, study & have sufficient funds and health insurance.

It’s because the US has the Derby Line which is in Vermont (Stanstead, Quebec) as it has a distinct border clearly marking which parts belong to Canada and the US (like that area is divided, taxed twice by both countries, and border checkpoints everywhere) but would an EU-style freedom of movement remove that by allowing citizens of both Canada and US cross freely (ID’s from both nations become valid travel documents).

However, that would need cooperation with both governments and opinions from the populace whether they’ll condone freedom of movement between Canada and the US (as in American people who live in Point Roberts, WA can cross into Canada as if it’s another state). That means Alaska is accessible for Canadians on a road trip who live in Yukon province (put it this way: both US & Canadian citizens can stay in either nation for 3 months).