[paragraft]

As a NZer I got thrown when going to California, by asking the front desk staff to do something and then waiting patiently when they said "I can't do that". Turns out when you come from a place where there's a vowel difference between "can" and "can't", that's what you listen for. I didn't at all pick up on the "t" sound at the end.

[robocat]

Here's an American saying and explaining the spoken difference between can and can't:

https://m.youtube.com/watch?v=o_GHV6RTy9c

I agree, it certainly sounds queer to my ear. She says can't has a short vowel, whereas in NZ English it is important that the vowel length is spoken long.