FDR confiscated all gold to thwart the Great Depression and fund the war effort, and froze bank accounts for a handful of days, a Bank Holiday. For better or worse, it would be much more difficult to do this with btc.
Let's hope we never get to test this hypothetical, because it might even be easier to confiscate BTC - certainly to merely destroy BTC, and thus raise the value of your own. When a physical force comes knocking, it's going to be tricky to resist sharing a key - and unlike physical stores of value, digital trails of ownership might make it quite a lot trickier to deny ownership; it really depends on how much information that occupying force has.
Also, it's trivial to freeze BTC accounts too; that just means controlling the network - which in the even of a physical occupation is going to be obvious anyhow.
Then there's the fact that occupiers may be able to engage in a 50% attack (assuming occupation is large scale and impacts many miners) - and may well force usage of their fork of the chain, even in absence of a global 50% control, making the whole thing rather tricky to predict.
Let's hope it never comes to that, but I'm certainly not convinced BTC would be immune from a physically occupying force's influence. I bet it depends hugely on the details of that occupation.
