Unfortunately, most of the streaming content providers (netflix, hulu, amazon, apple, itunes.) negotiate licensing rights to each country on an individual basis. That means that your account has to 'match' the country where you are trying to access the content; i.e. if you sign up for Netflix in the US, you can only watch content while you are physically in the US.
The content provider 'knows' where you are based on the IP address assigned by your internet provider. So if you try to watch NetFlix while connected to the web via TelMex, they know you are in Mexico and block the content. I think this is total BS, but thats just the way it is.
If you are a traveler, the main way to get around this is to use a proxy server, which allows you to route your internet traffic through a US-based server, which gives the appearance that you are still in the US. There are free proxy servers but come with security concerns- it is probably better to use a pay service-there are many out there, you just have to google it. If you are not a traveler but live in Mexico, it may worth it to investigate signing up for your streaming services via the Mexico branch of each company (I know NetFlix has started in Mexico, but I'm not sure about the others; and I'm not sure if the content would be 100% the same either- you would have to investigate)