When does ‘have nothing to do with’ extend beyond the local church body?

I Cor 5, Mt 18:15-17 and 2 Thes 3:6-15 speak of disassociating from unrepentant but professing Christians in the local body. Is it biblical to disassociate with an unrepentant Christian from a different church (thus under different leadership) who hasn’t been excommunicated from their own local church? How would a Reformed Protestant church answer this?