"Soda pop" is a bit of an antiquated term, at least in the United States. The general term used for a carbonated beverage is "soft drink" (as compared to "hard" liquor), and different regions have their own terms. People will say "soda" or "pop" (or "coke" in parts of the South), but one doesn't ever really hear "soda pop" together.
In Australia it's either "soft drink" or "lemonade". (Our lemonade isn't normally made of lemons, but means any sweet aerated drink, but most commonly clear). When travelling, I've found "soft drink" has become fairly universal, so would be the best international English translation. "Soda" in Australia means baking soda or bicarbonate of soda, two baking products. "Pop" means to go bang or is a common name for grandfather.
Actually from Swedish's limonad/lemonad (not sure if they still use either today), from the same French word English and many other languages got its version. It is sorta different things, sorta same. Some English speakers call the lemon flavoured carbonated drink a lemonade.
It is basically a generalisation, they got a flavour + style of drink combo (in many places the lemon and citrus based versions were the first fizzy drinks), but the "lemon-" part doesn't really mean anything, so they associated it to the style rather than the flavour.
Depends where you are, most people would say soda or cola (though cola refers simply to a dark "coca" like drink), and there are parts that would say just "pop". Living where I live, we have folks from everywhere and the term is just that (everywhere.)
Someone ordering a "soft drink" wpuld likely be them trying to sound proper and posh in a wierd way in the states.