The Mouse Guard rules are unclear on whether -- during an extended conflict, a team's actions specifically address only a single other team on each phase of the turn. I think so, but not everyone in my group agrees.
When multiple teams are involved teams should choose targets after actions have been declared.
Imagine the following three teams:
The following actions are declared:
After the actions are announced, the GM decides the Snake will target Team Kenzie with its Maneuver.
Everyone rolls dice.
These two posts cover some of this ground in detail:
Each action you target one team, but if that team is being helped or is helping, the other team takes the effect as well.
Anyone who shares your target with a vs must help you or you them.
Further, you do not script targets; you pick and announce target when you reveal script for that volley.
The rules for Multiple Teams, Multiple Actions (pg. 114) contain this line:
With that in mind, I have to assume that your action only affects one enemy team. If the action affected all enemy teams, they wouldn't need the "two teams have the same target" clause because everyone would have the same targets.