They completely control consensus when it comes to transaction ordering, but for other network parameters like emission rate, they don't have any control. If they decided to bump block rewards by 2x none of the blocks would be accepted by exchanges or merchants, and it would effectively be a hard fork. Segwit2x had majority miner support but failed because it couldn't get enough community support.
"Compliance measures on crypto-currency are expensive. We'll be charging a 3% compliance tax on all crypto-currency holdings, and we'll do this via any US-registered crypto-brokers charging a withholding tax unless you can prove it's double-taxation; also any failure to pay this is tax evasion and will be prosecuted as such"
you'll see some hard forks. Also this is a _great_ idea as it increases tax revenue, increases investment in US bonds and stocks, _and_ it suddenly swells the value of US Govt gold reserves.