Rust belt has been abandoned pretty much since Clinton... Nafta crushed it... Trump years helped, but 4 years of Biden have put it right back on the downward path.
PA is going to be interesting this fall. Trump should handily win the state, but PA GOP was a willing participant in the 2020 criminality, and unlike WI and MI which have made structural changes, GOP here did nothing... so While Trump should and would win PA in a fair election, the fact the GOP of PA let so much illegality and fraud go on in 2020 and did nothing about it, Trump will need a 5 point lead here before I would feel safe he can win.. unbelievable the fraud they let happen here.. and the GOP was an active participant in it.
I don't think Clinton or Biden have had anything to do with the demise of the Rust Belt. Time and internal political stupidity crushed it.
As one Congressional representative from Ohio pointed out at a conference I attended a few years ago: "It's not 'globalism' that's the problem when a company closes down an old steel mill in Ohio and opens a new one in Arkansas or Texas."