For the 100th time, Bitcoin is not anonymous. Bitcoin is pseudo-anonymous.
While in theory nobody knows if a certain address is yours, everybody can see all the transactions made with that address.
Similarly, if I buy cryptocurrency on the cash app and transfer it to my personal wallet, will this be considered a sale of my coins? How will the tax bureau track all this?
If you gave your details for one of the transactions your address is involved into, IRS can link that address (and related transactions) to your person.
Afaik no, but this depends from country to country and I don't know exactly how it is in US.