I am also American (born and raised in Chile). The Little Prince is extremely well-known over there. I am personally very fond of it.

I lived in America (NJ and CA) for 25 years and plenty of people knew about The Little Prince.

I've even seen people wearing shirts with the drawing of the snake that ate the elephant.

Apparently James Dean loved the book from an early age, so guessing it must have had some popularity in the USA.

It's not that obscure, even in the US. Anyone who takes French in US high school has probably read it in French (it's very easy to read), and even in English it's one of the most common classic children's books.

I live in the Netherlands for almost 50 years and never heard of it either.