technically you can buy crypto in the usa without having to report it. it's only when you exchange it for a different crypto or sell it for cash that you have to indicate that on your tax return by checking a box. of course, if you're using a centralized exchange like coinbase here in the usa, they do report to the irs so theoretically they could tell the irs every single transaction did using their service. including all your purchases.
bitcoin really needs a way to be transacted "off chain" so that prying eyes can't see what's going on just like you can use paper money without them knowing what you spent it on.... because right now, if you buy anything using bitcoin in the usa, well that's a taxable event that has to be reported. no one wants to have to do that and no one should HAVE to do that.
Indeed, it seems that the originally BTC was invented as yet another type of cash. It has many of the properties of physical cash. Its transactions are irreversible, wallets don't have owner's identity attached to them, you cannot lock the wallets, or invalidate coins, etc. It does not replicate all the properties of physical cash, but it is close enough.
However governments attempt to treat crypto wallets as yet another type of bank accounts and the crypto itself and electronic bank money. They will not stop until they regulate it to the point where it is no different from ordinary bank money.
Regarding the ability to transact bitcoin off-chain, I think that the closest thing to off-chain transactions that we have now for BTC is the Lightning Network which only stores aggregated transaction data in the blockchain. However this doesn't really solve the problem where you have to report all of your transactions to the government.
So this is yet another proof that governments treat crypto as yet another kind of bank money. There is one difference, though. With banks they can get a full list of your transactions to/from your account and with crypto this is not possible because they don't know taxpayers' wallets, so they shift the reporting burden onto the taxpayers.
For practical purposes there are two kinds of trades that governments cannot trace easily. The first kind are some of the online crypto<->crypto trades (DEXes, wallets that provide atomic swaps, non-KYC CEXes, etc.). And the other kind are P2P trades where the traders meet in person and exchange crypto for physical cash.