Not that I actually expect Kirill to ever play for Team USA, but I found this online:
Change of national eligibility (The ‘four-year’ case)
A player, who has previously participated in IIHF competition, can switch national eligibility (but only once in a player's life) if:
- He/she is a citizen of the new country of his choice
- A male player has participated for at least four consecutive years (1460 days) in the national competitions of his new country, during which period he has neither transferred to another country nor played ice hockey within any other country and has not played for his previous country in an IIHF competition during this four year period. For female players the period is two consecutive years (730 days).
- He/she has an international transfer card (ITC) that shows the transfer to the national association of the new country and which was approved and dated at least four years (two years for female players) before the start of the IIHF competition in which the player wishes to participate.