Some odd ones I encountered in Australia as a North American English speaker - that you pick up on quickly, but still seem out of place (that said, I use literally none of them myself):

- “How are you going?”. This is literally replacing ‘doing’ with ‘going’ for some reason. Took a second to pick up on this.

- “Heaps”. Pretty much a 1-for-1 swap with “Loads”. Though while we’d say “Shitloads” for extra emphasis, I haven’t heard “Shitheaps” in the same sense here. Otherwise, in most cases, it’s a straight swap. Pretty much instant recognition.

- “Do you reckon?” - Roughly “What do you think?/Do you think so?/Do you agree?” depending on the context/tone. Instant recognition (reckon is an archaic synonym for ‘guess’ in NAm, so just a little bemusement that this was the word used).

- “Mate”. Roughly equivalent to “Man” in North America, though used much more broadly. Instant recognition. Aside from the casual form of address between Males, I swear to God an Aussie could express a range of meanings equivalent to how the rest of the English speaking world uses the word “Fuck”. This second understanding of the word takes a bit longer living in Australia, and the first few years, one can find new expressions all the time.

- “How are you tracking?”. Really odd way of asking ‘how are you progressing’ (on some objective or another). Usually asked in as casual a tone as “How are you going?” but the intent is entirely different - which is why this one takes another second to realize that it’s different/ doing different work from the (socially intended/pleasantry) of “How are you going?”.

As mentioned before, I don’t use any of these myself - as it would seem out of place/I’m mocking them. I also generally don’t switch away from US pronunciations or spellings (as I already switched once from Canadian to US as a kid).