Explanation From Original OP:

An American general was stopped at the [Battle of the] Bulge [in WW2] by his own side who thought he was a spy when he correctly identified Springfield to be the capital of Illinois, but the soldiers thought it was Chicago. Not counterespionage work at it's finest...

It's that and pronouncing the S in Illinois when it's silent.

I once had a friend in college correctly identify that it's called the Windy City due to politics and everyone else in the immediate vicinity jumped to confidently tell her it actually because of the weather: *sigh*.

A better test would be to have them pronounce St. Louis. Eurpoeams tend to pronounce it the French way unless instructed otherwisr

It's Saint Louis as in the name isn't it

How do Americans pronounce it, Sent Lewis?

It is as in the name (which is pronounced as "Lewis", for us).

So "Saynt Lewis".

I... Are you being deliberately obtuse?

We don't say the "St." part different. Americans know it's pronounced Lewis, which Europeans try to pronounce it like the French monarchs