Which American mispronunciation of an English word annoys you the most?

The silent H in herb is actually correct. The word comes from Latin, where the H was already silent, and transitioned through old French where it stayed that way. When it reached English we also pronounced it without the H in the same way we don’t pronounce it in honour, or hour. It wasn’t until the 1800s when dropping an H in words was seen as a marker of low social class that a “hyper correction” occurred and people started using the H in error, in the same way that some people say “haitch” instead of “aitch” for the letter H. It was an attempt to sound more educated and for whatever reason it became the common usage. As recently as the early 1900s written examples of “an herb” exist.