Since when did Pokemon have nationalities? Only time I ever recall that being stated was Arcanine's Gold Pokedex entry, which said it was of Chinese origin.
America and France have also been mentioned in the games. Probably a few others too.
Lt. Surge is the Lightning American (I presume 'United States of'). Gastly can smother an Indian elephant. Mew was found in South America. Arcanine and Parasect get references to China. At Saffron City, an NPC is worried about being transferred to Russia. Fletching is a "Japanese Robin" Pokemon.
"Murder of the living is tragic, but murder of the idea is unforgivable." - Janus, speaker of the synod