Greenland has the population of a small US city.

For the cost of only $14 per American per year, we could pay everyone in Greenland $85k/yr for life. It’s $4.5/bln a year.

Greenland has already obtained some independence from Denmark and is looking for more. It’s unlikely they sell themselves to the USA directly but something that is effectively the same with a fig leaf on it could certainly happen.

And if actual world-scale conflict broke out, it would de facto be a US protectorate at best, and just another territorial acquisition at worst.