I'm probably the only person to get 19 right but miss Lake Tahoe. Well, now I know where it is. I probably had an advantage on this quiz, being from North Dakota.
That is correct, but in my area we use lake for the name and reservoir for what it is, as in, "Lake Wappapello is a reservoir on the St. Francis River."
I entered "Salton Sea" and when it grabbed this answer after "Salt" I thought that was a type-in for this answer - I only found out afterwards it gave the point for "Great Salt Lake", and Salton Sea was marked "wrong". That could be sorted out by requiring "Great Salt" as the Utah answer, that's how that lake is always known anyway.
That's the auto typein for the lake, so I don't think I should be the one to change it. Also, the Great Salt lake and Salton Sea are famous for being in Utah and California, respectively, so if a different place is filled in on the map than where you were trying to guess, it shouldn't be too difficult to figure that out.
I thought I did terribly, but apparently everyone struggles with this one. I at least got all of the ones over 50% and a most of those over 20%, so I guess that's a decent outcome.