By oppressive technology I am referring to the kind of tech that obviously oppressive governments would have built decades ago if it had been possible, and that the US will gradually arrive at soon enough without explicitly seeking to do so.

Let's think this through. How well has government prohibition of what private citizens do in their own homes worked in practice for anything else it's been tried on? Then consider that we're talking about data rather than physical objects, which are even slipperier.

All such an action would do is drive it underground. Anyone who wants to use bitcoin still will.