Do the Polish banks pull my American credit report
No. It's totally different in Europe.
or is the slate wiped clean in Poland?
So no slate to wipe clean. You'll find that credit scoring isn't as big a part of life. There's a register of debtors (debts within Poland) that a bank would check against, however they'd only really be interested in you having an income and legal residency.
You'll find that people use debit cards more than credit cards. People do get loans, however there is much less of a credit culture in PL.