Short answer here, make sure you call the correct file on index.html. I do everything in main.js and then compile into main.min.js, I was calling main.js when I should have been calling main.min.js
This solved the problem when requiring .jsx files into a single js file.
Hope this saves you a little bit of time.
ps - I tried everything solving this, there may have been another solution but I also had to make sure I had the correct dependencies installed