ASP.NET Core with EF6 Multiple Databases

I am currently trying to implement a solution with ASP.NET Core and Oracle EF 6. 

We currently have a single code base and database schema, but with 4 databases (one for each country).

I have genereated a EF Context, and created a simple partial class that implements a constructor taking a custom connection string. 

public partial class MyEntities
{
    public MyEntities (string connectionString) : base(connectionString)
    {

    }
}

In my appsettings.json file I have

"ConnectionStrings": {"MyEntitiesUS": "US Connection Information","MyEntitiesFR": "France Connection Information"
}

In Startup.cs ConfigureServices I have

services.AddScoped(provider =>
{
    var connectionString = Configuration["ConnectionStrings:MyEntitiesUS"];
    return new CIMSEntities(connectionString);
});

This works beautifully, and I can connect to the database. 

Typically we have grabbed the default database to connect to from a cookie or session variable, but I don't have access to either of those values in ConfigureServices.

So my end result would look something similar to the below:

services.AddScoped(provider =>
{
    string countryCode = //grab value from cookie
    var connectionString = Configuration["ConnectionStrings:MyEntities" + countryCode];
    return new CIMSEntities(connectionString);
});

Is there a way to accomplish this, without defaulting to US and having our France users have to reconnect on ever sign-in?