I think most could figure out that he was referring to people being disadvantaged from context clues, though.
In Europe they're almost certainly more likely to say "snookered" instead, as 8 ball is not their main sport.
US players generally understand that reference, but I'm not sure non- players will.
https://books.google.com/ngrams/graph?content=behind+the+eig...
Edit for comparison: https://books.google.com/ngrams/graph?content=behind+the+eig...
Search results include definitions such as:
"A term, referring to the game of pool, meaning in an unfavorable or uncomfortable position"
My Dad was born around the same time as Joe Biden (a few years different) and also from Pennsylvania (though I don't think this is particularly associatsd with that region) and used it fairly frequently; I also remember hearing it fairly frequently growing up fron others of his age cohort (and Boomers) and media created by and for them.
I think it's a fading idiom, though.