Belgium is part of the Schengen-area. Owners of a valid US Passport don’t need a tourist visa if their stay is under 90 days. Your passport must be valid for at least three months beyond your planned date of departure from the Schengen area. The 12-page U.S. emergency passport is not valid for visa-free entry into Belgium.
Flights to Belgium from the US
Currently there are no direct flights between the United States and Belgium. However it’s fairly quick and easy to find a connection between our neighboring countries that offer direct flights to the US. For finding the cheapest flight tickets I recommend using Skyscanner.
From London you can either take a flight or the Eurostar train to get to Brussels in about 2 hours. Alternatively you can travel to Amsterdam or Paris and take the Thalys or TGV trains which will bring you to Brussels in less then 2 hours. For more information check the page: Trains to Belgium.