That one sentence alone should dissuade anyone from calling America a democracy.
If America were a democracy instead of a Constitutional Republic then it would already be that way.
That's like saying "If England were a monarchy, then the Queen could decree any law she wanted for the country". Having a monarchy doesn't mean the monarch has absolute power to do whatever they want, and having a democracy doesn't mean the voters have absolute power to pass anything they want. In most cases, they decide things indirectly and delegate power to others. The electoral college is a perfect example of that.