Notes on Nationalism is quite different from 1984, more focused on its effects on the individual (obsession, self-deception, etc.) than tyranny per se. He makes the distinction between nationalism and patriotism and his use of term is a bit unconventional (for example he includes pacifist rhetoric as an example of what he calls nationalism).
I think defining the nation as simply "the decisions of a group" loses a lot of subtlety. E.g. what separates the term nation from country or corporation? Drawing on Benedict Anderson's Imagined Communities, I think identity, community, and mass communication play a big part in this.
An interesting contemporary example of the development of nationhood, was posted here a while back about the transformation of Taiwanese identity, from majority Chinese in the 80s to majority Taiwanese in the 10s.
Nationalism is simply the decision of a group, 'the nation' to constitute its own interests and to determine its own laws and rules, not automatically tyranny.
The idea of a global internet is inherently anti-democratic because it excludes the option that nations determine in a sovereign manner what cultural values or laws or rules apply to their communications infrastructure. Given that cultures and laws diverge drastically on speech, religion, privacy and almost anything else it was only a matter of time until conflict would arise.
Up until now it wasn't really a global as much as an American internet anyway, the difference is just that other countries are catching up and reasserting themselves.