Every nation in the world has place-names not in their original language corrupted into a form that makes sense in its spelling and pronunciation. It's a completely normal part of history. England's -wick and -chester/-ciester/-caster suffixes came from Latin -vicus and -castrum, for example. Moscow/Moskva came from a Finno-Uralic name the Indo-European Slavs took as the name.
Many American place names are NOT Anglicized in spelling and occasionally pronunciation, but thankfully they can be made so so fairly easily. Many names are already English in pronunciation and just need a spelling update (St. Louis = St. Lewis, New Orleans = New Orlins) Germanic languages despise vowels and case endings as a name's last syllable and will slice them off (Utraictum/Bonna/Londinium/Dovris = Dutch Utrecht, German Bonn, London, Dover) unless the second-to-last syllable is a long vowel (Normandia = Normandy), so Cincinnati, Philadelphia, Atlanta, Minneapolis becomes Cincinate/Sincinate, Philadelphy/Filadelfy, Atlant, Minneaple (a la Constantino-ple/Adriano-ple) in many "folksier" or "hickish" nicknames, pronunciations, or letter/diary/journal/record writings. Many Amerindian names already follow a de-facto anglicization in pronunciation and "folksier" writings, and just need a spelling update from a French form or drop the vowel per normal Anglicization rules (Arkansas, Missouri/Missouria, Mississippi, Chicagou/Chicagoua = Arkansaw, Missory, Mississip, Shicago).
You notice I speak on "folksier/hickish" forms a lot, it just turns out these supposedly-less educated people were Anglicizing non-English names all along into English forms naturally - I gleamed all the above forms from finding them so consistently spelled as such in records. It was our "elites" that wanted non-English, fancy new French/Greek/Latin place names to differentiate ourselves from England post-Revolution. All the Thirteen Colonies' original areas have either English or Anglicized forms everywhere, locals kept doing that but the bigwigs kept the French forms of Amerindian names in the Louisiana Purchase area or slapped Greco-Roman names down (which the hicks then Anglicized).
As a bonus, slicing off that last vowel syllable alongside English spelling as need be not only makes American toponymy CONSISTENTLY English/Anglicized (enough, in some cases)-looking, but makes them short and sweet enough to begin using as surnames a la European cities and towns, which furthered a sense of nationalism and culture. Imagine, say, Michael-of-Atlant, Gerald-of-Demoin, or Craig-of-Leweyville simply sloughing of the "of" to become Michael Atlant, Gerry Demoin, Craig Leweyville, etc. as normal American names like "Jack London" the writer had such a name, or "Clark Birmingham", etc. And when you get to THAT point? They're undeniably AMERICAN names, words, places. And no one would ever confuse them for any other people's homes.
