Iced coffee is one of the most common way to drink coffee in Japan. Not only in summer, many people drink even in winter.
There are cold coffee beverage in Europe too but it is not similar to Japanese iced coffee. Japanese one is a cold beverage with ice and cold/room temperature coffee. The importance is that the coffee is not hot or warm when pouring into the glass filled with ice cubes.
Then, ice coffee never comes with whipped cream or ice cream. In addition, it is usually not sweetened. You can pour milk and/or simple syrup called gum syrup which usually come separately.
Be aware when you are ordering a coffee. In Japan, coffee does not mean automatically "hot" coffee. Therefore shop assistants and waiters will ask you "hot or ice". Then, coffee with ice cream is called "coffee float".