Genealogy is certainly a journey.
While you have your ancestors in Yorkshire in 1790, you don't give a timeframe for when they emigrated to the US through Liverpool. Depending on the timing, there could be several explanations. After the Union of the Kingdoms, Scots often went where the jobs were and given the emergence of the industrial revolution that could be anywhere.

Given that in the USA it would have been an advantage during some time periods to be English rather than Scottish it would make more sense to claim an English origin if they could.

Again - just thinking out loud here.