Sorry, but: "On 1 July 1931, pilot Wiley Post and navigator Harold Gatty completed their circumnavigation of the world in a Lockheed Vega airplane, Winnie Mae, in 8 days, 15 hours and 51 minutes; the record for fastest circumnavigation was once again held by an airplane. This was 10 1/2 years before the Pan-Am Clipper is claimed to completed a circumnavigation. And it was a full circumnavigation, leaving from and returning to Roosevelt Field, Long Island, NY.
There were actually several before this, but not Americans.
If Amelia Earhart had completed her flight she would have simply been the first woman to do so.
Sorry but you didn't say non-stop, but the Pan-Am Clipper couldn't have done it non-stop either. To get across the Pacific the Clippers had to re-fuel at Midway Island, where Pan-Am had facilities. Oh, and you didn't define "commercial". The Lockheed Vega is by definition a "commercial" type, and since the Post-Gatty flight was sponsored by an oil company the flight itself could be termed commercial. If you had said "Being operated in air-commerce...." that would have changed things! AND, in spite of the term "Circumnavigation" being used to describe the Clipper's flight it strictly was not, since it concluded the flight some 2,600 or so miles from returning to the it's starting point!