Good morning Yohan! It's good to hear from you.
I know that it must have been incredibly difficult to translate in your mind and then try to write in English. I do understand you and have some answers for you.
In the US, surgical techs focus on setting up the instruments for the case, and assist the surgeons during surgery. They cannot assess, they cannot administer medications, they cannot take doctors orders, they cannot coordinate post op care for the patient. Their main role is to assist the surgeons in the sterile field.
The RN must coordinate all of those things. It's kind of like being the quarterback in American football, or the offensive midfielder in soccer. Just like a quarterback coordinates plays with his team mates, the RN does the same thing by coordinating pre-op care, ensuring correct documentation, gathering needed supplies, delivering to the field in a sterile fashion, monitoring staff for breaks in sterility, carrying out doctors orders, and communicating with the post-op nurse prior to the patient leaving the OR. You still have to take orders from the coach, because he runs the show, just like you have to take orders from the surgeon.
You as the RN are responsible for a number of things involving many different areas, like pre-op, intra-op, post-op, implants, pharmacy, critical care (if warranted), blood transfusions, etc.
Does that make sense? Where in South America are you located? Tell me about your hospital and what the work flow is like there.
I have gone on a few mission trips to Nicaragua, and the practice is VERY different there. The anesthesia techs were the ones that induced, not the anesthesiologist. That surprised me. They did not have surgical techs there, either. Just RNs, so I can see why you are confused about the different roles here in America.