I have my project structure set up to symlink local dependencies. Those symlinked dependencies also import css files. I have an example project linked below so you can see the issue reproduced. You can bundle with browserify just fine if you import the 'style.css' while working inside the 'styled-component' project, but if you try to use it as a symlinked local dependency using linklocal, you will get an 'Unexpected token' error as soon as it tries to read the css.

project
 main
 index.js
 node_modules
 styled-component -> ../../styled-component
 styled-component
 index.js
 style.css
 package.json

Link: example project