The problem with that glib-sounding notion is that, besides being, potentially, a chicken-and-egg issue, is that the amount of available, suitable land is much more limited than the vastness of, for example, the USA, would suggest.

The first could be solved by something like the UK's New Towns, although that requires a level of government involvement that is likely politically impossible in the US and perhaps Canada, as well.

The second is the more important issue, since, based on many of the comments, people don't seem to merely want to live nearby to another few thousand people. They also want lakes, forests, mountains, or some other geographic or natural feature. They also need provisions and Internet, which means pre-existing infrastructure nearby.