Bitcoin is governed by individual nodes. Currently there are at least 10K (some estimates up to 50K), many of them behind Tor.
Anyone can run a node if they are willing to devote enough storage to hold the timechain (blockchain) and a few hundred Kb of bandwidth per day. It can easily be done with less than $100 USD worth of hardware.
All of the software is MIT licensed (FOSS) and many people run older versions to ensure no malicious changes are put into updates.
Any node that doesn't agree with my node is simply ignored by my node. What we call the bitcoin network is simply all those nodes that agree on the same set of rules.
Miners compete to find blocks that are accepted by the majority of nodes.