To the extent that "White Anglo-Saxon Protestant" is a useful demographic category in American political studies to begin with, Martin Van Buren in 1836 really shouldn't be considered "non-WASP." "WASP" really should include "WASP-passing" and "WASP-adjacent" in most circumstances. The Dutch as a nationality/ethnicity are socially and culturally a
very close group to the majority-Protestant ethnicities of the British Isles, and the Dutch-Americans (even if possibly less so in the pre-Civil War Era than in the post-) are by far the most WASP-adjacent "white ethnic" population in the United States, with the possible exception of the French Huguenots.
Non WASP is less meaningful than non Protestant Northern European. The Dutch elite were pretty firmly in the WASP camp. FDR was Dutch but no doubt the most waspy POTUS.
FDR, unless you consider '"elite"/"rich" in America' to be an innately "WASP-y" category, was pretty far from being the "most WASP-y POTUS" (he's beat by literally every Republican President to date). Your post otherwise was 100% correct.
