But in terms of convergence - Wimpy was offering to repay Tuesday for the price of a hamburger today, back in the 1930’s. So “hamburger sandwich” may simply be a disappearing local colloquialism. Similarly, how often is “truck” used for “lorry” in the UK? Certainly “lorry” is barely understood in North America. I assume usage like this is picked up from global media.
(I should add that a lot of the content of Hollywood is explicitly chosen to be understood by the braodest audience. So for example, a truck will never be referred to as a “lorry” unless there’s a reason to make the speaker want to be speaking UK-ish. And they’ll put the body in the trunk, not the boot. And then these references over time become the standard wherever these shows are seen)
IMHO simplified English is a stepping stone to full English. It may take several generations, but comprehending the vocabulary is the first step to grasping the full language and grammar. Just as southern Americans try often to shed their accent that makes them sound like Dukes of Hazzard or Mayberry extras, others too will strive to sound like they “fit in”. As I understand it, 1800’s chinese pigdin is by now a distant memory and the locals speak the good engrish.
What I see as an interesting shift in English, though, is the emergence of TLA’s. (Three-Letter Acronyms). As might be expected from a country called the USA, where IBM was a big company along with RCA, GM and Esso (Exxon), we have simplified words like TV and lately, IED. Not to mention terms like 3G, ISS, NDA, POTUS, SCOTUS, etc. Not just that these are written shortcuts, but the spoken shortcut is entering the language.
you also have to distinguish between words that are current slang - shred, pwned, cast shade - versus words that are new concepts and likely to remain part of the language like cellphone, bluetooth, wifi, web page, synthesizer. The slang is likely to fade with time when it’s no longer groovy, daddy-oh…