A friend concurs:

As I recall, I think Lindbergh did think of American Jews as different
from other Americans, but he also seemed to think (at that time, at
least) that most Americans of differing backgrounds were different from
eachother too. He seemed to think that most ethnic groups comprised
separate ‘races,’ which is how he referred to the British, as well as
the Jews. And his closest friend most of his life was Harry Guggenheim,
who was the first person he visited after the death of his son.