Menú Desplegable con Buscador

Codepen

HTML

<html>
<head>
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<link href="https://cdn.jsdelivr.net/npm/select2@4.1.0-rc.0/dist/css/select2.min.css" rel="stylesheet" />
<script src="https://cdn.jsdelivr.net/npm/select2@4.1.0-rc.0/dist/js/select2.min.js"></script>
</head>
<body>
<select class="selectstate" name="state" style="width: 300px;">
  <option value="">Select State</option>
	<option value="AL">Alabama</option>
	<option value="AK">Alaska</option>
	<option value="AZ">Arizona</option>
	<option value="AR">Arkansas</option>
	<option value="CA">California</option>
	<option value="CO">Colorado</option>
	<option value="CT">Connecticut</option>
	<option value="DE">Delaware</option>
	<option value="DC">District Of Columbia</option>
	<option value="FL">Florida</option>
	<option value="GA">Georgia</option>
	<option value="HI">Hawaii</option>
	<option value="ID">Idaho</option>
	<option value="IL">Illinois</option>
	<option value="IN">Indiana</option>
	<option value="IA">Iowa</option>
	<option value="KS">Kansas</option>
	<option value="KY">Kentucky</option>
	<option value="LA">Louisiana</option>
	<option value="ME">Maine</option>
	<option value="MD">Maryland</option>
	<option value="MA">Massachusetts</option>
	<option value="MI">Michigan</option>
	<option value="MN">Minnesota</option>
	<option value="MS">Mississippi</option>
	<option value="MO">Missouri</option>
	<option value="MT">Montana</option>
	<option value="NE">Nebraska</option>
	<option value="NV">Nevada</option>
	<option value="NH">New Hampshire</option>
	<option value="NJ">New Jersey</option>
	<option value="NM">New Mexico</option>
	<option value="NY">New York</option>
	<option value="NC">North Carolina</option>
	<option value="ND">North Dakota</option>
	<option value="OH">Ohio</option>
	<option value="OK">Oklahoma</option>
	<option value="OR">Oregon</option>
	<option value="PA">Pennsylvania</option>
	<option value="RI">Rhode Island</option>
	<option value="SC">South Carolina</option>
	<option value="SD">South Dakota</option>
	<option value="TN">Tennessee</option>
	<option value="TX">Texas</option>
	<option value="UT">Utah</option>
	<option value="VT">Vermont</option>
	<option value="VA">Virginia</option>
	<option value="WA">Washington</option>
	<option value="WV">West Virginia</option>
	<option value="WI">Wisconsin</option>
	<option value="WY">Wyoming</option>
</select>
</body>
</html>

JavaScript

$(document).ready(function() {
    $('.selectstate').select2();
});

CSS

.select2 {
  margin: 0 auto !important;
  display: block !important;
  top: 30px;
}
.select2-container--default
  .select2-selection--single
  .select2-selection__rendered {
  color: #ccc !important;
  font-family: Arial;
}
.select2-container--default .select2-results__option--selected {
  background-color: #222 !important;
}
.select2-container--default .select2-selection--single {
  background-color: #333 !important;
  border: none !important;
  height: 38px !important;
  padding-top: 6px;
}
.select2-container--default .select2-results__option--selected {
  background-color: #222;
}
li.select2-results__option {
  font-family: "Arial";
  background: #333;
  padding-left: 15px;
  color: #ccc;
}
.select2-search--dropdown {
  display: block;
  padding: 4px;
  background: #333;
}
.select2-search__field {
  border-radius: 6px;
  font-size: 16px;
  height: 34px;
  padding-left: 10px !important;
  color: #333;
}
.select2-dropdown {
  border: none !important;
}
.select2-selection__arrow {
  top: 4px !important;
}