Bitcoin can be anonymous, but it isn't by design. There are a number of methods you can go through to increase your chances of remaining anonymous whilst using bitcoin, but these are of varying complexity and many users don't do this. If you are using bitcoin addresses which have ever been linked to your real identity (because you've completed KYC on an exchange), then you are not anonymous and the government can detect that fairly easily. Exchanges are being forced by governments to hand over details of their customers' trades, deposits, and withdrawals, meaning the government can then use blockchain analysis to track down your other addresses and activity. Unfortunately governments very much can still restrict people by banning exchanges from various countries and forcing mandatory KYC requirements. If you are using bitcoin as a means to avoid tax, unless you are taking additional steps to hide your identity, you are going to have a bad time.

Using a proper mixer such as ChipMixer is good step to take, but if you want to be fully anonymous then you are probably looking at running your own Monero node over Tor and not using bitcoin at all.