If the government can’t create Bitcpins out of thin air, then who does? Accounts are synced to a central server somewhere.
It takes a huge amount of computer processing to create a new bitcoin. That is, it costs money for high-end computers and the electricity to run them to produce new bitcoins (think of all the effort required to mine new gold).
Compare that with the Federal Reserve. The FR just moves the decimal point to the right and, voila, new money is created. The hard part for the FR is getting the “new money” into the Treasury.