According to Wikipedia, the Chicago metropolitan area has a population of about 10 million people, far less than Poland’s 38 million, which makes your claim completely impossible from the start. In fact, according to other articles, it seems that there are about 185 000 people of Polish descent living in Chicago (less than half a percent of the population of Poland), and a bit less than 10 million in the entire US (which is significant compared to the population of Poland, but still “only” about a quarter). And this article claims that there are “roughly 20 000 000 people of Polish ancestry living outside Poland” [in total], which is still less than the population of Poland.

Mali, not Malaysia, which has the .my suffix.

Just read the second (or the first, but that is more technical) link I shared. Some native speakers do in fact seem to say “should of” even when the “of” is stressed, so in their dialect it would be grammatical.

While it is true that “should of” etc. can easily originate from a confusion between “‘ve’” and unstressed “of”, which sound identical, the statement

“Should of” is incorrect

itself is at least a bit misleading and prescriptivist in its generality.

Interestingly, there seem to be at least some native English speakers who genuinely do say “should of” (with a stressed “of”) sometimes. This paper for example argues that people who say “should of” really do use a grammatical construction of the form modal verb + of + past participle. One argument the author mentions is that this would also explain the words “woulda”, “coulda” and “shoulda”, since “of”->“a” is quite common in general (e.g. “kind of” -> “kinda”), but “'ve”->“a” basically doesn’t occur elsewhere (e.g. no one says “I’a” or “you’a” instead of “I’ve” or “you’ve”). Another is that the reverse mistake, i.e. using “‘ve’” in place of “of” (e.g. “kind’ve”), is much rarer, which is a clear difference to e.g. the situation with “they’re”/“their”/“there”, where people use these words in place of the others in all combinations frequently. I recommend this blog article for a much longer discussion.

Also, whether genuine mistake (which it almost certainly is in many cases, although probably not all) or different grammatical construction, YSK that “should of” etc. didn’t just become popular recently, but have been used for centuries. E.g. John Keats wrote in a letter in 1814: “Had I known of your illness I should not of written in such fiery phrase in my first Letter.”. Many more examples (some older as well) can be found e.g. here or here.

TL;DR: While in many cases “should of” etc. can well be a mistake, originating from the fact that it sounds identical to “should’ve” when unstressed, there is some interesting linguistic evidence that at least in some dialects of English native speakers really do say “should of” etc. (i.e. in those cases it is not a mistake, merely non-standard/dialectal).