Well A lives in Canada while B lives in US. Good luck on suing A anyway. And it looks like business B was in charge of the Kickstarter campaign, not business A. B is responsible for the backer's money , not A. That's my understanding of facts so far.

You cant sue business A because business B was in partnership with business A but business B robbed you. A contractual obligations were toward B, not the backers. A didn't launch the kickstarter campaign nor was responsible for managing Kickstarter's money.