Where are you looking? This very well is likely regional. I grew up in the Midwest and every house in my neighborhood had at least two floors, usually more like 3 (ground floor, finished basement, 2nd story).

Communities built for older people often only have one floor due to mobility issues and parts of the country (most of the south) do not have basements. If you’re relying on film/television then it’s likely they’re not filming in the parts where basements are common.

In North America, cellars usually are found in rural or older homes on the coasts and in the South. However, full basements are commonplace in new houses in the Canadian and American Midwest and other areas subject to tornado activity or requiring foundations below the frost line.