I think that most believe the Fat Man is the most well know player in the USA. It's easy to prove walk into any bar and openly ask the question and before the night is through some one will come over and tell you a story or mention his name.
I also agree that there is a difference in how different age group's will answer the question and that the Black Widow is very well know along with others mentioned.
But, the reason that any of these people are remembered is because they were either self promoted or promoted by an organization. In my opinion the main reason that Pool is not where it could be today is a complete lack of player promotion and a good strong front man of women. Yes I am certain that a well made movie would help but combining pool with gambling also will not hurt.
I think the days are gone or should be gone where people are trying to promote pool as anything other than another form of gambling. I kinda think gambling is here to stay so maybe it is time to present pool from the Hustling stand point of view that it has been hiding and trying to change since the movie the Hustler hit the Golden Screen. I also think with that said and the right front person pool could be brought back in the main stream enough to bring it out it's current slump.
JIMO