I don't know who told you it was that simple, but the entire reason Nixon had to take us off the gold standard in the first place was because other countries were taking their World War 2 gold deposits out of US holdings and it was screwing with our economy. If it were as simple as what you said, we'd never have gone fiat in the first place.
Fractional reserve banking lets you grow past the limits of your gold reserves to an extent, but sooner or later, the amount of gold you have absolutely affects how much you can back your money with gold. Whoever told you otherwise was either lying to you or they themselves didn't understand the situation.
