Make use of Advanced Wheres. For your example, it'd be something like this:
->where(function ($query) {
$query->where('city', '=', city1)
->orWhere('city', '=', city2)
->orWhere('city', '=', city3);
})->where(function ($query) {
$query->where('country', '=', country1)
->orWhere('country', '=', country2);
});