We may be too diverse, different, and divided to stay together now, but I’d say that in the past we were one nation. Like other countries, we did have a recognizable national core with outlying minority groups. The big split was between North and South, but there was more agreement and unity in the (non-Southern White Protestant or Christian or Judeo-Christian) core than there is in today’s America.
The north were successors to the English freeholders and emerging bourgeoise class of merchants and manufacturers
The south were would be European noblemen. The relationship of nobles to serfs is quite similar to that of plantation owners to slaves, the main difference being that serfs were tied to the land owned by the noble while the slaves could be bought and sold. In overpopulated Europe, serfs had no cash value due to overpopulation - if you had land, the serfs came with it.