The difference between can in You can go. and can in That's a large can. is mostly because functional words like modal auxiliaries such as can, will, etc. are unstressed, so the vowel in the middle becomes reduced. While nouns like can, box, etc. don't show this reduction.
How much reduction and what the vowel in the noun is, does differ across English variants. Also the amount of nasalization of that vowel compared to the one in cat.
In case you want to check out the Yale American dialect atlas: https://ygdp.yale.edu/phenomena-by-category
Although it's mostly about grammatical