Latinos making jokes about their own culture during a comedy show where the audience knows and expects those kind of jokes from that particular comedian is very different from a presidential candidate's rally platforming a white man making "jokes" about PR being a floating trash pile, Mexicans breeding too much, and Black people carving watermelons instead of pumpkins for Halloween. If you don't understand that, then at least recognize that everyone else does.
Bad Bunny, Jennifer Lopez, Ricky Martin, and other PR celebs either shared the "floating garbage" clip (along with comments like "this is what they think of us" and "this is an act of disrespect") and/or shared Harris' proposed policies for PR, and endorsed Harris to their combined HUNDREDS OF MILLIONS of instagram followers. JLo alone has 250M followers.
trump's campaign has already disavowed the PR joke. "This joke does not reflect the views of President Trump or the campaign," Trump senior adviser Danielle Alvarez says. Florida Rs are in damage control mode. At least *they* know how many PRs live in an important electoral state (more than 1M).
As for whether this sways "undecided" voters - understand that an undecided voter, almost by definition, is someone who doesn't know enough about either candidate to make a choice. These are extremely politically disconnected people. They don't watch the news, read newspapers, or use social media for political info. Depending on their age, they might have been school children at the time trump's "grab em by the *****" tape leaked, they weren't paying attention to trump while they were in middle/high school. As hard as it is for you to believe, there are many such voters out there, who only learn about the political headlines that make the biggest splash and manages to breach their bubble. Or if their favorite singer posts about it on instagram. There's also plenty of voters who are "holding their nose" to vote for trump. The expression about the straw that breaks the camel's back exists for a reason. How many Black and Latino "nose holders" are going to feel motivated to cast their vote for a guy who lets some schlub "comedian" make jokes like this at their expense?
But sure, this was *not* an unforced error and in no way will this hurt republicans by one single vote. Also, 450K Puerto Ricans live in Pennsylvania. :-)