Update****
I did make it back to the U.S. after a big headache. Turns out their airport staff was not aware of these letters and it took them almost an hour to manually enter the new expiration date. The lady at the security check did not even bother to look at the extension letter at all. I had my fair share of panic attacks yesterday lol. I did however hear that British airways is always the strictest airlines to travel with. Once I tried boarding my flight, my boarding pass declined again, however, there was a really sweet lady who mentioned that she’s seen this before and she let me through. US immigration at LAX was thankfully super familiar with my letter and after asking me a few questions, I was able to return home ❤️
safe to say: I won‘t travel outside of the US, until my case is finalized.