Filtering: Displaying Records with Relationships in Another Table

I'm trying to create a list of event instances and want to filter them based on the country where the events will take place with Filamentphp.

I have three tables: event_instances, events, and countries.

• Each event_instance belongs to one event.
• Each event can have multiple event instances.
• Each event belongs to one country.
• Each country can have multiple events.
• I have a country_id column in the events table.

I have these relationships

class Event extends Model
{
    public function country()
    {
        return $this->belongsTo(Country::class);
    }
}

class Country extends Model
{
    public function events()
    {
        return $this->hasMany(Event::class);
    }
}

class EventInstance extends Model
{
    public function event()
    {
        return $this->belongsTo(Event::class);
    }
}

class Event extends Model
{
    public function eventInstances()
    {
        return $this->hasMany(EventInstance::class);
    }

    public function country()
    {
        return $this->belongsTo(Country::class);
    }
}

When I do this to verify if relations are successfully working.

$eventInstance = EventInstance::find($id);
$country = $eventInstance->event->country;

It also gives me this

App\Models\Country {#6998
    id: 2,
    name: "Aland Islands",
  }

I want to filter the dropdown menu of countries to only show the countries where events will take place. But it shows all countries in the countries table.

SelectFilter::make('country')
    ->label('Country')
    ->relationship('event.country', 'name')

What I am missing here?