(Like I said, it was just in a crossover video of the intro on YouTube. They actually didn't use Russia for every Death the Kid scene, they switched up the characters every time. For example, it showed America and Canada for Soul and Maka in the beginning part, then switched it to Taiwan and Hong Kong, then back to America and Canada. Same with Death the Kid. They had Iceland, Norway, and Denmark as Kid, Liz, and Patty, then changed it to Egypt, Turkey, and Greece, then switched it again to Russia, Ukraine, and Belarus for a different scene. The person was just trying to add every character into the video. Here's the video:
https://m.youtube.com/watch?v=Js0d1q3i7t4&list=FLu8xRQO3ZjOli_F8Bb6mXdA)
Russia"Yeah." Russia said to China, looking at his faucet pipe.