How to get id of model while doing store function in controller?

I'm trying to insert into two tables that are related through a many to many relationship, but I need the user id to pass to the related table, how do I get it?

This are the store and getCountry function:

public function store(Request $request)
{
    ini_set('max_execution_time', 300);
    $users = $request->all();

    try
    {
        DB::beginTransaction();
        foreach ($users as $user)
        {
            $dbUser = $this->getUser($user['USERNAME']);
            Log::error($dbUser);
            $dbUser->name = $user['NOMBRE'];
            $dbUser->user_name = $user['USERNAME'];
            $dbUser->email = $user['CORREO'];
            $dbUser->last_name = $user['APELLIDO'];
            $dbUser->password = $user['PASSWORD'];

            $this->isSet('TIPO-USUARIO', $user);
            $user_type_id = $this->getUserId($user['TIPO-USUARIO']);
            $dbUser->user_type_id = $user_type_id->id;

            foreach (explode(',', str_replace(' ', '', $user['PAIS-USUARIO'])) as $c)
            {
                $country = $this->getCountry($c);
                $dbUser->countries()->save($country);
            }

            $dbUser->save();
        }

        DB::commit();
    }
    catch (Exception $e)
    {
        DB::rollBack();
        throw new HttpException(500, 'My error message');
    }
}

private function getCountry($id)
{
    $country_id = Country::where('id', $id)->first();

    return $country_id;
}

The error i get right now is:

SQLSTATE[23000]: Integrity constraint violation:

1048 Column 'user_id' cannot be null (SQL: insert into user_country (country_id, user_id) values (1, ?))

via Chebli Mohamed