Peter Greenberg says this is the time for international travelPHOTO: A departures board with European routes departing from Terminal 7 at John F. Kennedy International Airport (JFK) in New York, U.S., on Monday, Sept 27, 2021. The U.S. will soon allow entry to most foreign air travelers as long as they're fully vaccinated against Covid-19 -- while adding a testing requirement for unvaccinated Americans and barring entry for foreigners who haven't gotten shots. Photographer: Angus Mordant/Bloomberg via Getty Images