OK, so what are the rules in the USA for "Louis"?

Examples

Joe Louis, (who I know as "Lewis", but most people in UK want to say "Loo-ey")

Louis Armstrong (hello Dolly, this is Lewis, Dolly),

St Louis, Missouri. "It's the ghost, of the Saint Lewis Blues" according to Leon Redbone, but Billie Holliday sings "Saint Loo-ey Woman")

and then there is Louisville, Kentucky.

Can somebody please 'splain.

cheers, Terry