Let us see what is this whole fuss about?
To an untrained observer both look the same. But to the ones who notice those pretty pretty hands can clearly demarcate the differences.
First up, the base tone differs. In a classic French Manicure pinky tone clear base is applied all over the nail and then a dense white tip is painted across the ends. Whereas in the American same look is imitated apart from usage of color using a creamy colored base, like a flesh skin tone, finishing off the tips with a hint of pink or even red in some cases - yet keeping it quite natural-looking.