I came across the following chart on the world’s busiest airports in 2018. Three US airports are in this list with Atlanta taking the top spot.The other two airports are Los Angeles and Chicago’s O’Hare.

Click to enlarge

Source: Explore the World’s 10 Busiest Airports, U.S. Global Investors

Though Atlanta consistently ranks as the world’s busiest airport, most the traffic is domestic and not international. London’s Heathrow is the world’s busiest airport based on international passenger traffic.

You can find many other fascinating facts in the above linked article.