As I recall (and I'm not looking this up, so someone correct me if I'm wrong): Mervyn was a young Canadian men's single skater when he was found by Richard Gautier and Bruno Marcotte and persuaded to skate pairs with Narumi Takahashi for Japan. He moved to Montreal to train with her, and the Japanese skating fed paid all the expenses for both of them. Japan has very strict citizenship requirements, and he didn't ever live in Japan, so there was never any question of his getting Japanese citizenship or participating in the Olympics.
What was surprising is that his partnership with Narumi ended in December 2012. There were lots of rumors about whether the fed has ended it or Narumi had. The most widely accepted story was that Narumi ended it so she could find a Japanese partner and go to the Olympics, and the fed tried to talk her out of it.
Mervyn then found a Canadian partner, Natasha Purich. There was idle speculation about whether the Japanese fed would release him to compete internationally for Canada, since they had such a latrge investment in him. If they hadn't, it would have been a very odd and perhaps unprecedented situation, since he is actually Canadian and always has been. Apparently they did release him, since he and Purich competed internationally for Canada.
His partnership with Purich didn't work out. There aren't a lot of unpaired pairs women in Canada, especially at his level. A lot of people think Kirsten Moore-Towers should have chosen him over Michael Marinao, but she didn't, or he didn't, or they didn't.
Anyway, he then paired up with his friend Marissa and they agreed to skate for the US but to train in Canada. Canada released him to skate for the US.
Given US citizenship laws, living in Canada pretty much guarantees that he will never get US citizenship. Unless there's an obscure US law I've never heard of that allows citizenship to be granted with no residency conditions. Perhaps by the President? Or by an act of Congress?