JSFiddle - React, Tailwind, and code Playground

HTML

<div id="video-container">
    <iframe width="1000" height="563" src="https://www.youtube.com/embed/U4oB28ksiIo" frameborder="0" allowfullscreen></iframe>
</div>
<p>This should stay right underneath the video</p>

CSS

#video-container {
    position: relative;
    padding-bottom: 56.25%;
    padding-top: 25px;
    height: 0;
}

iframe {
    position: absolute;
    top: 0;
    margin: 0 auto;
    left: 0;
    right: 0;
    width: 100%;
    height: 100%;
    max-width: 1000px;
    max-height: 563px;
}