JSFiddle - React, Tailwind, and code Playground

HTML

<iframe width="854" height="480" src="https://www.youtube.com/embed/C0DPdy98e4c"></iframe>

CSS

iframe {
  max-width: 98%;
}

JavaScript

responseveIframe();

function responseveIframe() {
  $('iframe').height(
    $('iframe').attr("height") / $('iframe').attr("width") * $('iframe').width()
  );
}

/*this functions is only needed to see the resize as you drag display border*/
$(window).resize(function() {
  responseveIframe();
});