Like what? Is it an issue with specific services/providers? Or total internet bandwidth? Anyone know the bandwidth the submarine cables can handle in their current configuration?
I don't think the backbone of the Internet cares about this. ISPs get a box with all of Netflix's content in it, so you probably never go out to the Internet to watch something on Netflix. (YouTube also does this, though obviously they don't cache every video in every local ISP's cache, and I believe that Apple has a system like this as well.)
If there is any slowdown, it is likely due to limitations in the last mile. Netflix isn't sending 4k video streams from California to everyone else in the world individually, assuming everything is working.
As others have noted, the problems are with specific ISPs and their underdimensioned last mile network and/or backhaul.
A modern submarine cable, like Google's new Dunant transantlantic cable, has 250 Tbps of bandwidth. For reference, the largest Internet Exchange in Europe, DE-CIX, just reported a new traffic record of 9 Tbps.
So, no, anything using fiber isn'ta bottleneck. You can fit all of DE-CIX traffic on a single strand of fiber with off the shelf gear.
It is usually ISPs oversubscribing their nodes to too many customers. DOCSIS 3.0 and 3.1 are very fast. The video services that work the best leverage locality so that you aren't steaming westword over the ocean, but from a local cache much closer to you.
What's the real bottleneck here?