Database
[{id:100,status:"ordered",country:"US",items:[]},{id:101,status:"ordered",country:"UK",items:[]},{id:102,status:"shipped",country:"UK",items:[]},]
Query
db.collection.aggregate([{$group:{_id:{country:"$country",status:"$status"},count:{$sum:1}}},{$group:{_id:"$_id.country",status:{$push:{k:"$_id.status",v:"$count"}}}},{$set:{status:{$arrayToObject:"$status"}}}])