Yeah junk food creates addiction over the time. Even more the "American junk food", which I can say, for example, to be a lot more "junky" than junk food you can find in Italy (where I live in), as I often travel to USA and I had the opportunity to see the differences (even if I am not a junk food eater, I only have it twice a month).
If you try to eliminate sodas and add fresh fruit/vegetables juices (not the sugar-loaded ones packaged, I say 100% fresh juices) and obviously water, and try some "healty alternatives" like sandwiches with seitan (or other vegan alternatives), without creamy cheeses and sauches, you may experience a little change in your diet
For me, as a not abitual junk food eater (I don't even eat sweets, I have them only once-twice a month), I completely don't feel the need of them, some of them even make me with a sense of disgust (that demonstrates, when you are addicted, you feel the need of foods your natural body would completely reject). With the sweets, I like them, however when I eat a sweet I feel it A LOT sweet more than other people may experience: if you eat too many sweets, you are too familiar with the "sweet taste" and you don't even manage your body maybe is refusing such an amount of sugar. When you are addicted to junk food, your psichology wins over your body, and your "need" of junk food completely bypass your body's reaction to them.