A small point: Everybody knew the Earth was a sphere. It had been known for over a thousand years. The notion that Columbus was butting against a prevailing flat earth orthodoxy is a 19th century invention.
Yeah, that line is a little strange b/c of the lack of context. This piece is taken directly from the book “The Miracle and Magnificence of America.” The chapter begins with a cartoon reference to a flat earth that derides biblical “fundamentalists” (like Columbus).