I partly disagree. I think the concept separate independent networks is very fundamental to internet, and as such BGP etc are fundamental part of the internet.
It's fundamental to how it's set up currently but not required for the concept as a whole. Given a global telecom operator BGP could be eliminated, so it's a 'lower' level of fundamental than TCP.
If there was a global telecom operating "the internet", it wouldn't be a internetwork of independent networks, which I consider fundamental concept for the internet.
It'd still be an interconnected network of machines. But this is really just coming down to the dividing line between a network and the internet, kind of like the heap of sand paradox. http://en.wikipedia.org/wiki/Sorites_paradox
