The amount of resources that it would take for governments to fully control cryptos is astronomical.
it's just a scare tactic. most people can be scared into compliance, and i'm sure that's the intention here. the u.s. government is definitely smart enough to realize that they can't realistically control cross-border payments with cryptocurrencies.
i'm really curious to see how courts would interpret "possession" in this context. merely possessing a private key is not physical possession of funds. the fact that many people could have access to a single private key seems problematic. if five people have access to a key with $10k on it, are they all required to declare? if so, the law is illogical. what about multi-signature wallets?
anyway, in this context, cryptography will become increasingly important. i'm going to get in the habit of "encoding" an HD wallet seed (12 words) manually throughout handwritten notes/schedules/calendars. only a trained eye who is familiar with the seed should be able to recognize it. brain wallets for the win!