The Oil Drum

Do you have any idea how useless modern lawns are for growing anything other than that monoculture green carpet? Rebuilding a real soil system of any depth takes years. It's one reason I use raised beds instead of trying to til nearly dead lawn with only an inch or two of soil under it anyway.

Likewise with planting fruit trees. Most of my fruit trees are a few years away yet from providing any serious harvest though the orange tree may give me a few oranges this year.

This is not something that can be done instantly, overnight or via mail order and a Fedex shipment for tens of millions of people. Then there is the problem of learning your local environment, its pests, its growing season(s) and the oddities thereof.

It would all be likely to happen over a long time-scale and very informally - deteriorating suburbs, dereliction and arson, and any would-be developer could simply arrange another 'accidental' fire to get rid of the remains of houses in the areas he was interested in, then buy the land as wasteland.

I doubt that they would or could go to the expense of bringing in topsoil, just work around the houses, or maybe rake the existing topsoil a bit thinner.

In reality though, I can't see the land even being used as farmland in the States, they would just be abandoned.

The only reason agricultural land is in relatively short supply in the States is because of high meat consumption and subsidies for the ethanol scam.
The money in the scenario drawn would not allow for either, so no development of waste land would likely take place as agricultural land would not be in short supply absent these.

It's a different matter in Europe with land in much shorter supply, but then again suburbs there are less extensive.