It’s totally fair to assume this song is in C minor. Sure, C minor chords shows up here and there, and much of the melodic content could be attributed to the C minor pentatonic scale. I wouldn’t blame anyone for thinking this song is in C minor.
The U.S. was founded on Enlightenment principles, and many of our deepest assumptions about art and life come from the era after Bach’s lifetime. Although Bach’s music is universally loved now, the stern Lutheran beliefs that infused its creation are counter-cultural today, and have often been ignored or derided since his lifetime. These days, the idea that theology can find direct expression in music theory can seem at best a heady curiosity, and at worst a regression to a way of conceiving the world whose very nature challenges some of our most cherished cultural, social, and political achievements.