I cringe on tours when people say the stupidest things or ask the most embarrassing questions that show the traveller has not taken one minute to learn about their destination.
As an Australian, one gets tired of the jibes “all of Australia came from convicts” which ignores the 60 000 years of human settlement followed by the waves of migration from Europe and Asia in the last 230 years.
Standing in the Forum in Rome listening to people confuse Greece and Rome or ask if the Colosseum was built in the Middle Ages is enlightening in a negative sense.
Last year in Berlin, I met people who were stunned that the Berlin Wall had in fact in Berlin. They were convinced it had been built in Russia (at least they had heard of Russia, I guess).
Wikipedia has a history section on most cities and countries on the planet. Ten minutes spent reading up on an overview will prepare most travellers to sound smarter than we are! (but don’t be a know it all either! That gets tired!).