because the Panama papers was mostly a non-event for US folks. FATCA was already in full force. that a few celebrities who have money had accounts there ... means nothing.
it was a big thing for countries where the leak uncovered (or "proved") corruption.
Because US corruption is not hidden. There's nothing to uncover really. It's done in plain sight. There are two dedicated people for that for each state on the federal level. There are complete industries sustained by nothing but endless subsidies. Already super favorable tax regulations, already great ways to store wealth in ways that are conveniently inaccessible to public eyes.
Of course if by fix you mean putting an end to economic rent-seeking, then for that the way forward is healthier markets and/or "whatever the Nordic countries are doing".
it was a big thing for countries where the leak uncovered (or "proved") corruption.