So someday we might see the secret service enforcing rules about how much computing capacity any one entity can control; to prevent collusion attacks on widely used cryptographic ledger systems?

I think the most likely outcome is that governments will become the largest miners to secure blockchains. The security of a blockchain is a public good.

There's no need to regulate computing capacity when you have the power to tax enough wealth to ensure that the government always has more computing capacity. It's an arms race without the nuclear winter, and with the side effects of increased pollution and rapidly advancing processing power.