How would you know what the most common mistakes are with Chilean speakers of English? Do you speak in English much to Latinos? I've met a great deal of foreigners, and I am most impressed with the English of continental Europeans. South Americans don't tend to have great English, and neither do Asians, where Japan seems to have the best speakers, disregarding pronunciation.
I have a few Chilean friends, and they do tend to make a lot of mistakes.
And just in case you think that your English is perfect, you should know that it is not. Here are some corrections:
"like an poorly" should be
"like a poorly"
You should have a comma like so:
"excuse my poor english," since
"excuse my poor english", since
depending on style guide. Basically, you need a comma there.
"poorly educated American would fool people"
"poorly educated American, you would fool people"
Missing comma and not reiterating the subject (you) in the second clause.
In fact you are an arsehole for judging where someone is from simply from how they typed. Guessing is fine. Making a solid judgment and believing it to be true... not so fine. You are a complete idiot in fact.
From your obnoxiousness, I am certain that you are not human, and would never believe you otherwise. Humans just aren't that stupid.