In American English, the article “an” is used for a vowel sound to separate the words so they don’t blend together when speaking.
Normally, “a” always precedes a consonant, while “an” precedes a vowel. But “an” also precedes vowel sounds - i.e., the sound of the letter of the beginning of a word.
An apple
A banana
An hour
Hour starts with a consonant, but is pronounced with a vowel sound at the beginning. Thus, it is not “a hour” and rather “an hour”.
In the case of the example from the meme, id argue that either article works:
A “I’m…” - Typically when speaking, a person has a brief pause before they begin the quote. Since that pause would be enough to distinctly indicate two separate words, this sounds fine when being verbally spoken.
An “I’m…” - Looks great in text and would be the correct way to list it grammatically. However when speaking this aloud, since the person would have a brief pause when saying “an” and then the quote, it probably wouldn’t sound as great to some others.
My take - I like “an ‘I’m…’” best. Both in text and verbal form. Others may disagree as far as verbally said; however, grammatically in written form this is how it should be.
Edit: Fixed the inevitable autocorrects from typing this on mobile.
Because different dialects pronounce herb differently, sometimes the ‘h’ is pronounced, sometimes not.
I know you specified American English, but even within American English, you can find areas that differ on this, and I’m sure there are other words where this kind of thing crops up.
Also, I guess this may be worth mentioning as well:
Though this no longer seems to be as common as it was 10-20 years ago…
“An hero.”
Sometimes, either an unintentional misuse of this a/an rule will be ironically copied, and more widely used, essentially to either mock the original usage/user…
… or the a/an rule can be intentionally misused, as a way of infantilizing yourself, trying to come off as cutesy/ditzy, or maybe play up your own awkardness or inexperience, something like that.
In American English, the article “an” is used for a vowel sound to separate the words so they don’t blend together when speaking.
Normally, “a” always precedes a consonant, while “an” precedes a vowel. But “an” also precedes vowel sounds - i.e., the sound of the letter of the beginning of a word.
Hour starts with a consonant, but is pronounced with a vowel sound at the beginning. Thus, it is not “a hour” and rather “an hour”.
In the case of the example from the meme, id argue that either article works:
My take - I like “an ‘I’m…’” best. Both in text and verbal form. Others may disagree as far as verbally said; however, grammatically in written form this is how it should be.
Edit: Fixed the inevitable autocorrects from typing this on mobile.
This does get confusing with say…
“A/An herb.”
Because different dialects pronounce herb differently, sometimes the ‘h’ is pronounced, sometimes not.
I know you specified American English, but even within American English, you can find areas that differ on this, and I’m sure there are other words where this kind of thing crops up.
Also, I guess this may be worth mentioning as well:
Though this no longer seems to be as common as it was 10-20 years ago…
“An hero.”
Sometimes, either an unintentional misuse of this a/an rule will be ironically copied, and more widely used, essentially to either mock the original usage/user…
… or the a/an rule can be intentionally misused, as a way of infantilizing yourself, trying to come off as cutesy/ditzy, or maybe play up your own awkardness or inexperience, something like that.