JSFiddle - React, Tailwind, and code Playground

HTML

<select id="asset_id" name="asset[asset_id]">
        <option value=""> - Select Trailer - </option>
        <option value="1">Trailer 1 - Spanish</option>
        <option value="2">Trailer 1 - English</option>
        <option value="3">Trailer 1 - French</option>
        <option value="4">Trailer 1 - German</option>
        <option value="5">Trailer 2 - Spanish</option>
        <option value="6">Trailer 2 - English</option>
        <option value="7">Trailer 2 - French</option>
        <option value="8">Trailer 2 - German</option>
    </select>
    <br />
    <select id="country_id" name="material[country_id]">
        <option value=""> - Select Country - </option>
        <option value="11">England</option>
        <option value="12">Spain</option>
        <option value="13">France</option>
        <option value="14">Germany</option>
    </select>

JavaScript

var ddl1 = document.getElementById( 'asset_id' );
    
    function updateCountry ( e ) {
        
        var asset = this.options[ this.selectedIndex ].value,
            countryDDL= document.getElementById( 'country_id' ),
           country, i = countryDDL.options.length - 1;
        
        switch ( asset ) {
            case "1":
                country = 12;
                break;
            case "2":
                country = 11;
                break;
            case "3":
                country = 13;
                break;
            case "4":
                country = 14;
                break;
            case "5":
                country = 12;
                break;
            case "6":
                country = 11;
                break;
            case "7":
                country = 13;
                break;
            case "8":
                country = 14;
                break;
        }
        
        for ( ; i > -1 ; i-- ) {
            
            if ( countryDDL.options[i].value == country ) {
                countryDDL.options[i].selected = true;
                break;
            }
            
        }
        
    }
    
    ddl1.onchange = updateCountry;