These figures come from the National Science Board, which has published a report that contains "a broad base of quantitative information on the U.S. and international science and engineering enterprise."
The full report is on their website and is quite detailed.
This excerpted table contains data showing how students in various countries responded to the same questions, which makes for more direct comparisons:
The tomato genes question is my favorite.
And this table compares scientist vs. public opinions on several STEM topics. It's quite interesting to see by how much the numbers differ in the two columns: