JSFiddle - React, Tailwind, and code Playground

HTML

<div class="d1">
  <div class="video-container">
    <div>
      <iframe src="https://www.youtube.com/embed/Vbg81kc56FU" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
    </div>
  </div>
  <div class="text">
    Test
  </div>
</div>

CSS

.d1 {
  background-color: #f1f2f4;
  display: flex;
}
.video-container {
  flex: 1;
  background-color: red;
}

.video-container div {
  position: relative;
  padding-bottom: 56.25%; /* 16:9 */
}

.video-container iframe {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  display: block;
  width: 100%;
  height: 100%;
}

.text {
  flex: 1;
}