The scale seems to be slightly off at very-close locations.
I had 4 guesses all within 1 mile of the location, but then the flag is many times further away from my guesses than the "1 mi" scale shows.
https://img.incoherency.co.uk/4472
I like this game very much. I don't know enough about the US to play it properly, but I enjoy playing it as partly a geometry problem, and partly a case of looking for Googlable clues in the photos.
There is a weakness because the images are loaded straight from Wikipedia: sometimes the filename of the image gives the location away, and even if it didn't I expect it's not too hard to get the metadata off Wikipedia given the image filename.
You might say "well don't look at the filename if you don't want it spoilt", but I often want to open the image in a new tab so that I can zoom, and then I accidentally see the filename.