No, the Nissan Leaf was not available in the U.S. earlier than Tesla's first car, the Roadster.
Tesla Roadster (First-Gen) was introduced in 2008 as the first highway-legal electric car with a lithium-ion battery and a significant range (about 245 miles per charge).
Nissan Leaf launched in the U.S. in December 2010, becoming the first mass-market all-electric car.
So, Tesla entered the U.S. EV market before Nissan, but the Leaf was the first mass-market EV, whereas the Roadster was a high-end sports car.
