I think I’d switch that from “quickly” to “eventually”, or “have a head start to” - we could get grid independence “relatively” quickly if the government subsidized it (I highly doubt first Gen fusion competes with natural gas or solar cost-wise), but a large amount of energy is used in transportation, home heating, etc.. Until those become fully electrified you’re still stuck in the fossil fuel economy.

There is no more reason to believe that than about fission. Fielding practical fusion would cost more than fission, and fission is not today competitive. (Some people are spending others' money trying to make fission competitive.) Unless somebody comes up with a copious supply of cheap tritium, it can have no substantial effect here, though it might be useful for outer solar system exploration.

But building out solar, wind, and storage will very predictably achieve energy independence, for radically less expense. No breakthroughs needed, but gratefully applied where found.

Can fusion power generation be made to work cheaply? Each day the question becomes less relevant.

Fusion could end up being a useless waste of effort, not a strategic imperative.