Bitcoin cannot be destroyed easily. The Bitcoin network is being secured by everyone from poor people in garages to big mining farms run by companies. So it would take a UN resolution and global enforcement to get rid of Bitcoin since it is geographically located everywhere. This is something that just won't ever happen. If Bitcoin is ever 'destroyed' it will be caused by people naturally leaving it. For example, if government(s) create their own cryptocurrency that is better than Bitcoin. If the USA made a decentralized but yet 'official' crypto that offered mining rewards or something, people would jump ship and get in behind the official government backed crypto. Another real threat I could see down the road is advances in computing. Once Bitcoin addresses can be hacked (eg. guessing a private key), the whole network becomes insecure. It then won't matter how many miners there are or anything else. The whole network will simply be insecure and people will leave it. I see this as a real threat, but not any time soon.
Here are my thoughts to your points.
1) Countries do not want to do this because Bitcoin is competition to their fiat currencies. Bitcoin takes power away from them and of course they do not want this. Whether Bitcoin is considered legal tender or not is also unimportant in my opinion. It's like saying water isn't a legal drink, but all humans drink water. Since Bitcoin is being used by people all over the world in both online and offline places, it does not even need officially announced.
2) I agree with this. Bitcoin sometimes works on it's own timing and seems to do it's own thing. This isn't necessarily a bad thing though. If prices are uncontrolled, this is exactly what we need. We don't need a government or a group of bankers having control over it. We don't need some authority trying to make it more stable. As Bitcoin grows and become more wide-spread, the price stability will follow.
3) This is a good thing for Bitcoin investors now though. It's good to get in while still early.
