No states have this requirement, and it's unclear if such a requirement would even be legal.
One of the core issues the Voting Rights Act addressed was the use of literacy tests, civics tests, intelligence tests, etc. which were frequently employed by southern states to systematically disenfranchise black voters there. The act contains language (in section 2) which prohibits any voting law that has a discriminatory effect, regardless of what the actual intent of the law is. That language lends itself to very broad interpretation, since it does not define what a discriminatory effect is or what outcomes would be acceptable.
Furthermore, it's politically untenable to get such a measure passed given the current controversies surrounding race relations, police brutality, illegal immigration, etc. Consider voter ID laws which several states have passed in recent years. They are consistently struck down by the courts on the "discriminatory effects" argument even though it's an unambiguous requirement that you must be a legal U.S. citizen to vote.
Most Americans would agree that it's pretty egregious how a significant portion of the voting population doesn't even have a basic grasp of how their own government works. However, it's impossible to rectify that problem because there will always be an argument at the ready that any such solution would disenfranchise some voters somewhere who, for whatever reason, wouldn't be able to pass that test.
Also note that the links provided in @Drunk Cynic's answer only deal with high school graduation requirements, not voting requirements (which, in my opinion, should be so patently obvious that I'm shocked we actually need laws to make it so -- how have we been letting people graduate HS without knowing at least that??)