The key differences are that Bruce Lee was an actor.
Mayweather is a world class professional boxer, who's spent his entire life fighting the absolute best there is in a FULL contact (with the fists at least) combat sport. He would just slip and counter and KO Lee in an instant.
Honesty you lot are very much blurring film fantasy with reality. Honestly fella's you can't catch bullets with your teeth.
Bruce Lee was an actor but don't confuse him with Jackie Chan, neither was Bruce Lee a fighter but don't confuse that with an inability to fight. While there is a lot about Bruce Lee thats open to question and many aspects that can never be proved either way he was undeniably extremely fast and very capable at reading his opponents (see what Joe Lewis has to say on the matter). There is every reason to believe he could credibly have been a worthy opponent to Mayweather. Infact glorifying Mayweather is almost as bad as people confusing film fantasy with reality.