I think this kata is a bit outdated, it would be nice to keep it up to date. The official recommendation after React 16.8 is to use functional components. Quick updated response:

import React, { useState } from 'react';

export function States() {
  const [united, setUnited] = useState(false);
  
  const unite = () => setUnited(!united);
  
  const message = united ? 'Code for everyone' : 'Make America code again';
  
  return <div className="status">{message}</div>;
}