I doubt the FBI would have a list, they have enough on there hands in the States...
A Canadian agency might track that information...
are you KIDDING me?? no law enforment agency is going to track who watched the video.. the numbers range in the millions.. the resources and man hours needed would be INCREDIBLE!!! and our LE is under staffed as it is.. not to mention any actual "perps" that deserve to be followed were probably behind 5 proxies.. and how are they going to track every source.. the video was on so many different sites, not to mention the deep web..