Qwes

<select id="country"></select>
<select id="city"></select>

const countryEl = document.querySelector('#country');
const cityEl = document.querySelector('#city');

countryEl.innerHTML = data.map(n => `<option value="${n.id}">${n.country}</option>`).join('');

countryEl.addEventListener('change', function() {
  cityEl.innerHTML = data
    .find(n => n.id === this.value)
    .cities
    .map(n => `<option value="${n.id}">${n.city}</option>`)
    .join('');
});

countryEl.dispatchEvent(new Event('change'));