This is a very simple question that can be answered by looking at the history of Bitcoin.
The most generic but also correct answer is that Bitcoin was started on the internet, not in a particular country since the creator was an anonymous person or group of people.
The more detailed answer is that on November 2008 the official bitcoin repository was created on SourceForge, and from there the development started by the open-source community.
In January 2009 Block #0 (the Genesis Block) was mined by Nakamoto and Bitcoin Version 0.1 was released. Also the first transaction took place between Hal Finney and Nakamoto.
So in conclusion we can say that this decentralized system (bitcoin) was started from another decentralized system (the internet).
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