Database
[{ids:{abc:[{name:"Ted",country:"US"},{name:"Matt",country:"DE"}],cde:[{name:"Lisa",country:"US"},{name:"Tina",country:"CA"}]}}]
Query
db.collection.aggregate([{$set:{ids:{$objectToArray:"$ids"}}},{$set:{ids:{$map:{input:"$ids",as:"item",in:{k:"$$item.k",v:{$filter:{input:"$$item.v",cond:{$eq:["$$this.country","US"]}}}}}}}},{$set:{ids:{$arrayToObject:"$ids"}}}])