It was Theodore Geiger the author of this statement. By this, he meant the Marshall Plan advanced both American and European economies.
The Marshall Plan was a United States' plan to help Western Europe to recover from the destruction caused by World War II, thus "doing well by doing good". The financial aid the US sent to Western Europe was rewarded with increased economical relationships with European countries and with the spreading of American culture in Europe which helped the US to sort of keeping it as an influence zone.