One of the idea behind CDN for javascript/css is to leverage caching by reusing the same resources across websites. But then optimization tools said we should bundle everything into one javascript, which delay the loading time, but defeat the initial purpose.
I wonder if the caching could be more intelligent, by recognizing libraires bundled into the "big" javascript that website delivers, and parse only the new content.
Bundling everything together is best, unless the cases where it isn't and you need some kind of file to be shared globally. Not necessarily in a global WEB context; just the site's own context works too. You want assets to be cacheable.
Regardless, big libraries on CDN's don't make as much sense nowadays as it did maybe 5 years ago. It's not like everybody is still using jquery. There's too many different mainstream libraries, with too many versions.