MILAN — On both sides of the Atlantic, migrants flooding across borders by the hundreds each day have met a hostile reception and governments unable to agree on how to cope with the arrivals. In Europe, where far-right parties have joined the governments in Italy and Austria and made gains elsewhere, even the most basic decision of which port would accept a ship filled with migrants has been fraught. On Tuesday, yet another rescue boat loaded with migrants struggled to find safe harbor in the Mediterranean, while in Austria police cadets playing the role of desperate refugees rattled a chain-link fence demanding to be let in as part of a high-profile training exercise to test the mettle of a new border force charged with preventing an influx of migrants. “We have had migratory crises in the past, but that is not what we are going through now.