Remembering Sioux Falls to Sioux City forms a little tail around 4 states helps. Or remember Nort Dakota is more boring looking than South Dakota is another easy way.
The low Virginia score is pretty surprising. It has one of the most distinctive shapes, a fairly high population, and significant cultural/historical importance to the US that you would think that the vast majority of people would be able to identify it.
As a Virginian myself, I was surprised as well, however, it's not as popular of a state as Texas or California which every non-American knows about, so I can understand getting it mixed up with Kentucky.
Scoring
You scored 10/15 = 67%
This beats or equals 18.6% of test takers
The average score is 13
Your high score is 10