On the heels of the confusing statement by the President ostensibly banning flights from Europe other than the U.K. for 30 days, but really banning entry for the next 30 days by non-U.S. residents who have been to the Schengen area of Europe in the past 14 days, the State Department is now warning against all global travel.
The Department of State advises U.S. citizens to reconsider travel abroad due to the global impact of COVID-19. Many areas throughout the world are now experiencing COVID-19 outbreaks and taking action that may limit traveler mobility, including quarantines and border restrictions. Even countries, jurisdictions, or areas where cases have not been reported may restrict travel without notice.
While the new policy does not go into effect until Friday at 11:59 p.m., and does not in fact restrict flying between the U.S. and Schengen countries of Europe, large numbers of international flights aren't going to be sustainable in the face of a ban on entry by most Europeans, and in the face of the government warning against travel on top of United reporting that net bookings (new minus cancellations) for Europe and Asia already down 100%.
Airlines will be adjusting their schedules quickly and removing flights from their schedules and in many cases bringing aircraft and crew home as they 'scramble' to understand the implications of administration policy. There's a non-zero chance Europe retaliates in kind.
My recommendation: Given government policy uncertainty it would be a good idea, if you're an American traveling abroad, for you to arrange to return home as quickly as possible before it becomes more difficult to do so.
As of this writing there are seats available on U.S.-bound flights. However if that changes consider flying to Canada and connecting, or if flights between the U.S. and Canada become problematic terminating your journey in Canada or Mexico as close to a major border crossing as possible and entering over land, picking up from there with a flight home.
It is not my intention to be alarmist however the latest moves by the U.S. government may be extremely disruptive I've been writing for days that my concern about international travel has been getting back. For the most part that concern was related to the possibility of being quarantined wherever I went as the cause of drying up flights rather than U.S. policy however that's where we seem to be.