I usually take British Airways when travelling to Europe (which airline I do recommend), and some of the stew staff speak with such strong Cockney accent that I don’t understand them when they propose chicken or beef, or ask if i want ice with my tomaHto juice.
Maybe because of my mom and her relatives, I can understand most English accents without much problem. After 50+ years, my mom has taken on the American version of most pronunciations I think. For instance, she doesn’t call a “vie-tuh-min” a “vitt-uh-min or “uh-loo-muh-nim” “al-you-min-ee-um”. I remember when I was 10 and visiting over there and I thought I was pretty cute. My great granddad asked me what I wanted to be and I told him a model. He couldn’t understand what I was trying to say and after several attempts of me saying over and over a model thinking he couldn’t hear me, I got quite embarrassed and flustered. Finally my mom came to my rescue and a great aunt explained to him that I wanted to be a mannequin.