This sums up my experience travelling and living abroad.
To your point on vocab choice: if I use vocab not present/with different meaning in American English I would get blank stares so I often switch to the American term e.g. mobile phone vs cell phone.
To your other point about local slang: I recently learned South Africans call traffic lights "robots", which I thought was fantastic.
I had a similar experiences to you on both accords:
1. It wasn't until a class aged 14 where I heard the word 'chasm' spoken aloud and realised I had it wrong all those years.
2. It took me a some time to realise a word which sounded like 'rederick' was actually rhetoric.
A few months back I opened a link to a new article using an in-app browser (no ad-blockers). I kid you not, upon initial load the entireiy of the screen was ads or "annoyances". The one thing missing was the entire reason I clicked on the link.