See, as someone who doesn't live in Europe, I honestly have a hard time telling which horizontal/vertical striped lines of red/white/orange/blue/black/brown/whatever, represent which countries. All I know is: that's not the flag of France. I have no idea which country it's for.
I also have trouble with all but a few of the country codes (the two letter notation for a country), and states by their letter codes, with few exceptions... for countries, I know like.... CA is Canada, US is the USA, UK is England/United Kingdom (and I know those are two different things, but I don't know why or how they're different). For States I know like... NY for new York and CA for California.... and like DC for Washington DC (which is different from the state of Washington).
Apart from that and maybe a few others, idfk. And yes, I did not do very well in geography class....
In any case, this joke almost went over my head and I'm still not sure whose flag that is.