An eternal debate in these United States. Is it soda? Is it pop? Is it coke?
A little bit of background. I grew up in Toledo, Ohio- the majority of people around me referred to it as "pop", and on as a generic term for "carbonated beverage" I did as well. Why would I or anyone else call it anything differently? It's what we heard all the time, and had no reason to call it anything else.
I, for the most part, however, called every soda by name-if it was a Coca-Cola, it was Coke, if it was Pepsi, it was a Pepsi. If it was Root Beer, I called it either "root beer", or (as necessary), by the specific brand. More often then not, I called each and every individual root beer by the specific brand I was referring to at the moment. I never asked my parents to get me "pop" when they went to the store, and I always specifically said I wanted "Dad's", "A&W", "IBC", "Barq's" or "Mug"(which my 3 year old daughter affectionately calls "doggy soda"). I was a huge Root Beer fanatic, and still am. I'm a huge purist as well, as I don't consider Birch Beer to be a type of Root Beer at all-too distinct of a flavor for me.
Anyways, back on topic. I started off calling it "pop", but after watching thousands of hours of television I noticed that the majority of people on screen referred to it as "soft drink"(something that is too general a descriptor for my needs), and/or "soda". Of course, I knew that it was "soda pop", but since I had always known "pop", it seemed natural to call it that. Then, when I was about 15 or 16 I had a friend that only called it "soda", and I slowly just made the transition. Low and behold, 7 or 8 years after that I ended up in Bellingham, Wa-where it is almost evenly referred to as "soda" or "pop"(breaking slightly more towards the "soda" category. Long story short, I end up "fitting in" regardless of my company.
Because of the differences in location, however, my daughters like to tell me that "Grandma Melody has Pop, and we have soda...I want "pop" like at Grandma Melody's!"
I even have relatives in the south who literally call it "sodey pop", and that bugs me to no end. It sounds even more hickish when spoken by someone without a redneck accent, however, so there is always that I guess.
In my mind, it doesn't really matter what you refer to it as in the states-everyone is going to understand you one way or the other, and only the most persnickety are going to call you out on it. Go with your gut and call it what you will. Either way, you will enjoy it(or not) all the same.