jQuery - Several select menu options make a field show/hide

Answer 1

How about:

$('select[name="country"]').change(function(){
  if ($(this).val() === "United States" || $(this).val() === "Canada")
  {
    $('select[name="state"]').show();
  }
  else
  {
    $('select[name="state"]').hide();
  }
});

Answer 2

$(document).ready( function(){
    $('select[name="country"]').change( function(){
        var thisval = $(this).val();
        if( thisval !== 'United States' && thisval !== 'Canada' ) {
             $('select[name="state"]').hide();
             $('#textfield').show();
        } else {
             $('select[name="state"]').show();
             $('#textfield').hide();
        }
    });
});

Answer 3

AND

$('select[name="country"]').change(function(){
  if ($(this).val() === "United States" || $(this).val() === "Canada")
  {
    $('select[name="state"]').show();
    $('input[name="text-field"]').hide();
  }
  else
  {
    $('select[name="state"]').hide();
    $('input[name="text-field"]').show();
  }
});

Answer 4

jQuery!

  $(document).ready(function() {
    $("#textfield").hide();
    $("select[name=country]").change(function(){
        if($(this).val() == 'United States' || $(this).val() == 'Canada'){
            $("#textfield").show();
            $("select[name=state]").hide();
        } else {
            $("#textfield").hide();
            $("select[name=state]").show();
        }
    });
  });