it will work without js ?

Hi,

Try like following

<select name="country_id" required="1">
    <t t-set="countries" t-value="request.env['res.country'].sudo().search([])"/>
    <t t-foreach="countries" t-as="country">
        <option t-att-value="country.id">
            <t t-esc="country.name"/>
        </option>
    </t>
</select>
<select name="state_id" required="1">
    <t t-set="state" t-value="request.env['res.country.state'].sudo().search([('country_id', '=', country_id)])"/>
    <t t-foreach="state" t-as="state">
        <option t-att-value="state.id">
            <t t-esc="state.name"/>
        </option>
    </t>
</select>

Regards