In pg. 3 of this interview by R' Hamburger שליט“א, he asserts in the name of the Michtav miEliyohu (Dessler זצ”ל) that the character of each nation's non-Jewish majority affected the temperment and expression of its Jewish inhabitants.
What is the source of this in Michtav miEliyohu and what (if anything) is his source for this assertion?