I would argue that for this to become even remotely possible, America's list of enemies must not automatically become everyone else's enemies too.
that is to say: the USA's secondary statutes have to become ineffective.
To do this, the EU's blocking statutes (to ignore secondary sanctions) have to be effective. Right now Europe's own companies just ignore the statutes to keep their US trade.
To make the blocking statues effective, the EU's own research recommended fines/sanctions/bans/… on licences for foreign (read US) banks, and companies that ignore the statue and don't serve EU companies trading with sanctioned countries.
But to do that, the EU would need alternatives to American services.
Power and influence follow sovereignty.
€0,02