PARIS — Soon after it became clear that more than 70,000 Moroccans were attempting to cross into the Spanish enclave of Ceuta — many by swimming across the narrow stretch of water separating it from Morocco — 22 European Union member states called on European Commission President Ursula von der Leyen to convene an emergency meeting of the bloc’s interior ministers. But before the meeting could even take place, Italy announced that it was temporarily suspending visa-free travel from Spain and reintroducing border controls. The irrationality of this reaction reveals the extent to which the migration crisis is eroding European unity. Over the past decade, it has fueled the rise of far-right movements that have learned to exploit anti-immigrant sentiment for political gain, while also undermining trust among European governments whenever one of them comes under pressure. Italian Prime Minister Giorgia Meloni, increasingly worried about her diminishing electoral prospects, has led the charge against Spain, imposing border controls rather than showing solidarity with a fellow Europea