Most arable land is privately owned, and most of those owners would fear vast numbers of squatters, just like the ranchers did 150 yrs ago. If you moved onto someone's property without permission, you would be breaking a law if they found you and objected. As with dogs chasing or killing livestock, they might revert to the SSS rule (Shoot, Shovel, Shut up).

Other uninhabited lands are owned by the government, which might overlook a bunch of squatters, esp if they had no way of enforcement.

A local problem causing survival migration would be enough of a problem on all sides, but some kind of large regional disaster would probably be a nightmare, and the longer it lasted, the worse it would be.

Most people who think about possibilities like this are really thinking only about themselves or including mostly a like-minded group of friends/relatives/neighbors. But the reality would be far from that.

The three most populated counties immediately east of Puget Sound here in WA are Snohomish, King and Pierce, with a total population of approx. 3.5 million people. Suppose something bad happened in that area (esp with warning), and all those people migrated east into the foothills of the Cascade Range.

Most wouldn't have shelter with them, most wouldn't have much food with them, and the local water sources would quickly become more fouled than they are now.

Combining the usual lack of preparedness with the national attitude of entitlement, it would get nasty very quickly. By the end of the first week there would probably be bodies rotting all over the place. YUCK!

Sue