JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="right">
    <input type="submit" />
  </div>
  <div class="left">
    <input type="text" class="textbox" />
  </div>
</div>

CSS

.container {
  width: 300px;
  border: 1px solid;
}
.left {
  width: auto;
  background: red;
  overflow: hidden;
}
.right {
  width: auto;
  background: blue;
  float: right;
}
.textbox {
  width: 100%;
}
@media only screen and (max-width: 300px) {
  .right {
    float: none;
  }
}