Any half decent collection of American folk songs should give you as many 'Scots' songs as you could possibly want, though describing them as of Scots origin is not necessarily accurate.
To start at the beginning of Cox's West Virginia collection 'Folk Songs of the South' you have; lady Isabel and the Elf Knight, Earl Brand, The Twa Sisters, Lord Randall, The Cruel Mother, The Three Ravens.......... et al
Likewise with 'British Ballads From Maine' (Barry, Eckstorm and Smyth)
You could do worse than to get hold of the Texas Gladden CD from the Lomax collection where you will heaar a number of them superbly sung.
Jim Carroll