Magento: Disable state/province option in checkout onepage

You have to edit 4 files:
- /checkout/onepage/shipping.phtml
- /checkout/onepage/billing.phtml
- app/core/Mage/Customer/Model/Adress/Abstract.php
-/skin/frontend/default/default (or your skin)/js/opcheckout.js
billing.phtml:
Comment out this Part:

<div><code> <div class="input-box">
 <label for="billing:region"><?php echo $this->__('State/Province') ?> <span class="required">*</span></label><br/>
 <select id="billing:region_id" name="billing[region_id]" title="<?php echo $this->__('State/Province') ?>" class="validate-select" style="display:none">
 <option value=""><?php echo $this->__('Please select region, state or province') ?></option>
 </select>
 <script type="text/javascript">
 $('billing:region_id').setAttribute('defaultValue',  "<?php echo $this->getAddress()->getRegionId() ?>");
 </script>
 <input type="text" id="billing:region" name="billing[region]" value="<?php echo $this->htmlEscape($this->getAddress()->getRegion()) ?>"  title="<?php echo $this->__('State/Province') ?>" class="input-text" style="display:none" />
 </div> </code></div>
<div>
shipping.phtml
The same:

<div><code> <div class="input-box">
 <label for="shipping:region_id"><?php echo $this->__('State/Province') ?> <span class="required">*</span></label><br />
 <select id="shipping:region_id" name="shipping[region_id]" title="<?php echo $this->__('State/Province') ?>" class="validate-select" style="display:none">
 <option value=""><?php echo $this->__('Please select region, state or province') ?></option>
 </select>
 <script type="text/javascript">
 $('shipping:region_id').setAttribute('defaultValue',  "<?php echo $this->getAddress()->getRegionId() ?>");
 </script>
 <input type="text" id="shipping:region" name="shipping[region]" value="<?php echo $this->htmlEscape($this->getAddress()->getRegion()) ?>" title="<?php echo $this->__('State/Province') ?>" class="input-text" style="display:none" /></div></code></div>
Abstract.php
Comment out:

<div><code> if ($this->getCountryModel()->getRegionCollection()->getSize()
 && !Zend_Validate::is($this->getRegionId(), 'NotEmpty')) {
 $errors[] = $helper->__('Please enter state/province.');
 } </code></div>
<div>
opcheckout.js
There are a few code-blocks you have to comment out.
Around line 330:

<div><code> if (window.billingRegionUpdater) {
 billingRegionUpdater.update();
 }</code></div>
<div>
Around line 440:

<div><code> shippingRegionUpdater.update();
 $('shipping:region_id').value = $('billing:region_id').value;
 $('shipping:region').value = $('billing:region').value;
 //shippingForm.elementChildLoad($('shipping:country_id'), this.setRegionValue.bind(this)); </code></div>
Around line 450:

<div><code> setRegionValue: function(){
 $('shipping:region').value = $('billing:region').value;
 },</code></div>
<div>
Around line 490:

<div><code> if (window.shippingRegionUpdater) {
 shippingRegionUpdater.update();
 } </code></div>
<div>

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