That's not what Webster's dictionary says. A capitalist is someone who has capital for investment. Would you agree with that definition? It certainly does not imply that a salaried worker is not a capitalist. Every person with a 401k is a capitalist by this definition.
It's true you don't have to be a socialist if you are not a capitalist. But in terms of `ist's, what else would an American likely be? A communist?