How do you seize fake property that doesn’t actually exist. Wait...how do you own fake property that doesn't exist in the first place?
Your bank accounts are just numbers in the bank's electronic ledger. All it takes to seize an account is access to the bits of data needed to move the contents to a different account. As for how much it is worth, it is worth whatever people are willing to pay for it on the speculative assets market.
The dollar doesn't have a fixed intrinsic value either, it is also only worth what the market thinks it is worth. This is one of the reasons why we get inflation whenever the dollar's value is getting challenged or just because the economy is adjusting to absorb excess free cash flow. Governments around the world injected trillions of dollars into the world economy to power through covid disruptions and now the global economy is adjusting to bleed those trillions of dollars out of circulation so we get an inflation spike.