Probably referring to dust bowl era land like Oklahoma. I don't like the word collapse, but I'm guessing there are implying that the ground is x% less productive for crop production or grazing).
The risk of land collapsing is probably greatest West of the Missouri river where historic rainfall is less and historic topsoil is less (Dakotas, Nebraska, Colorado, Kansas, etc).
Overuse of fertilizers can cause chemical burn which damages the soil ecology. In combination with tilling it will gradually destroy the soil quality.
Pesticides destroy insect diversity, including predatory insects that keep pests in check. This is particularly problematic because pest populations tend to recover more quickly than predator populations, so if you stop spraying the problem comes back worse. Pesticides can also harm bird and amphibian populations, which play a role in pest control.
Maybe not what they are referring too, but you can absolutely 'brick' land by over applying chemicals ('salting the earth'). There is a continuum depending on which chemical and how 'bricked' you make it.
Dave Montgomery posits that soil degradation has determined the lifespan of past civilizations. At the rate that plowing erodes soil it takes about 1000 years to deplete the resource to the point of desertification.
Where has this happened?