"Americans pronounce English wrong" is an absolute MEME. Not only does pronunciation change naturally over time even when a language is isolated to a single community, but modern American English is technically more conservative to Shakespearean English spoken at the time that the colonists split off than modern English RP. American English (for the most part, excluding some New England accents) is rhotic, and on that principle alone is closer to English spoken 200 years ago.

Even if it weren't, there's no "right or wrong" in language or pronunciation. By that same logic we're all speaking a horribly corrupted mix of Latin, French, and other Germanic languages, which are in turn horribly corrupted from older languages. That's how dialects and languages form. So we can stop arguing about how to pronounce "aluminum" or "aluminium" maybe??