In a different world, it would be interesting if Russia still controlled Alaska.

Canada and the US would have an immense land border with Russia. For centuries the US and Canada have basically only had friendly neighbours, how would it change if there were a land border with a hostile power?

For Russia, what would supply and communications lines be like? As it is, Russia’s far east is just barely connected to the main parts of Russia which are all right near Europe. Alaska would extend that across an ocean. OTOH, with the oil in Alaska, maybe it would be relatively heavily populated and relatively rich. Maybe Russia would be a weird country with two big rich provinces, one right next to Europe, one 12 time zones away right next to North America.

The US and Canada haven’t only had borders with friendly countries for centuries. Even as recently as the 19th century, the US was frequently at war either with Canada and the UK, Mexico, or the native Americans in the modern-day Midwest and western US.