US President Joe Biden "overstepped his bounds" by labelling Donald Trump's supporters as "garbage", according to University of California Political Science Professor Louis DeSipio. President Biden was criticising a comedian from Donald Trump's recent Madison Square Garden rally who referred to Puerto Rico as a "floating island of garbage". "The only garbage I see floating out there is his [Trump] supporters," Mr Biden said. Speaking to Sky News Australia, Professor DeSipio said President Biden "overstepped his bounds today and took the narrative away from Vice President Harris."