Three weeks post-Brexit, Europe and its markets are still spinning. The latest victim is Italy, whose banks hold billions in bad debt. Eurocrat rules prohibit a government bailout, but anything less would wipe away the retirement savings of Italian bondholders. The standoff forces the EU into a dilemma that could cause a “systemic banking crisis on the Continent,” writes Dr. Lawrence Lindsey, a former Federal Reserve governor and chairman of the Council of Economic Advisors under President George W. Bush. In a private memo to clients, he portends more problems for Europe — and the euro.