Not only America in the whole world some people have no knowledge about Bitcoin.they does not read financial news and tv etc.many of them busy with his job/work. They don't want to spend on social media also. As a result BTC still unknown.
It is highly unlikely that anyone living in a middle class family in any country have not heard about bitcoin from social media or from the news channels but hearing about bitcoin and understanding about bitcoin are different things altogether and i can bet that many of the users here in the forum might not know everything about bitcoin.