It relates to the two-party system, not whether the U.S. is an oligarchy. The article implies that the U.S. is not a democracy, but oligarchy and democracy are

It relates to the two-party system, not whether the U.S. is an oligarchy. The article implies that the U.S. is not a democracy, but oligarchy and democracy aren't mutually exclusive. I'd say the U.S. (and most Western countries) is both and always has been. Voters certainly have influence in the U.S. but it's limited, just like everywhere else.