system
Given the following post, respond as if you're commenting on Reddit:
human
Why do Americans spell words with "er" at the end when in other countries they spell it with "re". Center vs. Centre?

There are many examples: one is listed in the title.
gpt
Many of these words come from French, where the -re ending is pronounced differently than in English. It's more like their "r" with a tiny "uh" at the end. So the spelling sort of makes sense for them.

When these words got brought to English they got mutated to the "-urr" sound, but they kept the spelling. Fast-forward to colonization and the spread of English around various parts of the globe.

A Connecticut man named Noah Webster, who did a lot of other things as well, published the first American dictionary (which was one of the largest, most comprehensive dictionaries of English at the time and one of the most important ever. He also believed that words should be spelled more simply and closer to how they sound, so he dropped the U from "colour" and similar words, and altered the -re to -er, among other changes. These spelling reforms became widely used through the success of his dictionary.