Across cultures

I will be studying abroad this summer in Italy. In our orientation meeting we learned that the culture is very different in Italy and Europe than it is in the US. This is true for different places all over the world. In Italy you cannot touch the clothes in a store when you are shopping, you must ask first. I even learned in my management class that in Germany it is considered flirting when a cashier smiles at a customer. Everything from body language, to phrases, to food and just simple ways of acting can mean completely different things in different places. What I really find interesting though is how all this was created? Who decided what is appropriate and what isnt appropriate to do in a specific society. We all represent the human race, yet we communicate in different languages and create different standards. Can these cultures ever change or will they stay with that region forever? What does it take to change this?
After asking these questions, the answer is not clear. However, maybe the answer is that even if we could change them, there is no reason to. I have learned that when you travel to a foreign country, you should try and adopt their culture as much as possible and respect their ways. And anyways, the difference between cultures allows people to belong to a smaller society than just the entire human race.