The bubbles can’t form on their own, they need a little pocket to start the formation in. These pockets are called nucleation sites. Adding the ice introduces more of those, and mentos do as well, if you are familiar with “diet coke and mentos”
The reason you notice is more in room temperature soda, rather than cold soda is because the solubility of gas decreases in a warmer liquid, so the CO2 is more ready to become a bubble in warm soda rather than cold soda.
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