Hi OliviaClark! All entrants in the team must be US residents. If a team is selected as a winner, they will have to sign an affidavit and tax documentation, which is why the contest is for US residents only.
Viewing post in US residents only rule
Having global prizes is a standard set by most game jams originating from the US. GameName, ThatGameJam, I could go on. If they aren't even willing to let a US origin resident distribute the prize to the rest of the team, surely it is normal to think they might have some ulterior motive in play with such a restriction, considering the burden falls on the receiving participant...