JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <iframe class="iframe-class" src="http://www.cnn.com/"></iframe>
</div>

CSS

.container {
    width: 100%;
    height: 250px;
}
.iframe-class {
    width: 100%;
    height: 100%;
    border: 1px solid red;
    overflow: auto;
}

JavaScript

$(function () {
    setIFrameSize();
    $(window).resize(function () {
        setIFrameSize();
    });
});

function setIFrameSize() {
    var ogWidth = 700;
    var ogHeight = 600;
    var ogRatio = ogWidth / ogHeight;

    var windowWidth = $(window).width();
    if (windowWidth < 480) {
        var parentDivWidth = $(".iframe-class").parent().width();
        var newHeight = (parentDivWidth / ogRatio);
        $(".iframe-class").addClass("iframe-class-resize");
        $(".iframe-class-resize").css("width", parentDivWidth);
        $(".iframe-class-resize").css("height", newHeight);
    } else {
        $(".iframe-class").removeClass("iframe-class-resize");
    }
}