The FAA defines the airspace where drones are allowed to fly and generally, as long as they are not within 5 miles of an airport, they can be flown up to 400 feet above the ground and even up to 400 feet above a structure. So if you're not next to an airport, the FAA allows flying next to a skyscraper.
There is no existing mechanism for the FAA to monitor if there are drone pilots, licensed or otherwise, who will fly above this altitude limit. That is well and fine until you get into a close encounter with a manned aircraft, for which you could be facing heavy penalties if the FAA can identify you as the drone pilot.
Special Travel Considerations for ForeignersWhether you plan to fly for fun or for work, you must register your drone with the FAA using the FAADroneZone portal. If you plan to fly your drone for recreation in the U.S., you must take The Recreational UAS Safety Test (TRUST) required by the FAA.
Non-EU residents visiting EuropeYou also need to train and pass the drone pilot's certificate online exam and get the European certificate in any EASA Member State. Some National Aviation Authorities offer the training and exam in English. And of course, you need to comply with the European Drone regulations.