Castles consisted of walls (bailey/enciente) and a gatehouse as a minimum. In other words, a stockade or fort. Which are scattered all over the USA, even if they no longer stand in their original form.
The earliest castles were just timber walls, earthworks or a combination of both. The fancy stone and/or brick ones came much later.
No.
Earliest stone castles were simultaneous with earliest wood and earth castles. Like Langeais and Doue-la-Fontaine.