Classically, Congress held the power of the purse, able to both bar and require spending. This imposed a significant limit on Presidential power. With a bought court supporting him, Trump would have significant ability to essentially chart power as a king.
The reason states have more powers than the federal government is to test different methods of government and see what works best, then apply those lessons everywhere.
Turns out the red states consistently wind up much worse than the blue states. But they’re so brainwashed and poorly educated, they don’t learn from observing better outcomes elsewhere.