If you are American, you probably think that lemonade is the same thing no matter where you live. However, that is very much not the case. The sweetened lemon water drink that is served in the US is probably not what you will receive if you order lemonade in other countries. On the contrary, you will probably get a processed soda like Sprite instead of a homemade drink.
If you are looking to order a lemonade while traveling abroad, maybe ask for some details before, just to make sure that it is the same thing that you are looking for.