If Dollar dies, everything dies. Simple as that.
Simple Logic: If bitcoin was better than Dollars, why does everyone freak out when we see a crash? If bitcoin was that good, you wouldn't give a fuck about the price drops right?
Well, do we care about the USD's drops? We do, because it matters after all. Many currencies depend on it, and like you said.. if it's down, everything will be. Bitcoin is important too, and can take part in a very strong decision: digital or paper currency.