We might be short on land the majority views as attractive enough to actually live on. Rural Wyoming is by no means short of land, but it's dry, desolate, windblown, and hundreds of miles from any regions with, say, hospitals, or airports, or actual grocery stores, or land that can grow something other than grass, or other frivolities of modern living. The fact that land is divided up into huge ranches is, therefore, not a huge loss for people looking for a little spread of their own; the only way the land could possibly be economically productive is in those huge ranches. A lot of it's owned by the Federal government, as well.
So it's trivially supply-and-demand, and the fact is the US, at least, has a huge supply of land for which there is essentially no demand. It's been allocated about as efficiently as it's going to be. Canada has a similar situation. Does that mean we're not short on land? Technically, perhaps not, but realistically, if the land is effectively unlivable, it might as well not exist for our purposes.
On the gripping hand everyone has a different definition of 'livable', even to the point of some people being willing to live in rehabbed ICBM silos in the wilds of North Dakota.