Currently, if you use jsx in a React component in a .js file, like in https://glitch.com/edit/#!/wistia-next-app?path=components/wistia_embed.js:8:6, the syntax highlighting will break.
Why not just use the .jsx extension instead, since that’ll highlight with no issues? Excellent question!
Projects that use Next.js cannot use the .jsx extension. I don’t understand the reasons very well, but here’s the issue: https://github.com/zeit/next.js/issues/200.