Which region should I apply for with a BSc in my case? US, Europe or Canada?
I can't answer your first question, but can give you a bit of background that might help you figure out the US. 

First, is that the US doesn't have a national educational system. Some States have policies that cover many (not all) universities within that State. Other places and the other universities have their own policies, with only some oversight. So, your second question depends on the university. Some professors can influence the decision, especially if they have funded labs. Some can but won't. Some can't. But contacting the professors is generally a good thing to do as you get a bit of visibility and maybe some information about continuing. 

Second, is that if you get an offer of acceptance that doesn't include funding, you can either turn it down or try to negotiate for that funding. Nothing is very certain unless you are invited to join a funded lab. But in general, nothing is assured until you actually have everything in place. 

It is a shame I must give this advice, but this isn't the most opportune time for someone from Iran to be coming to the US. It was much better in the past, and I hope it will be better in the future, but I assume you read the news. Your other options may be better politically, though, among actual academics in the US you are likely to be welcomed. Good Luck.