So we basically have to put our faith and trust into machines that by doing computational expensive operations just for the sake of making them hard to break, will trade wasting a lot of energy for a little more trust.

The point is always "make it hard so it will be too expensive to crack it". but what if some country (or group of countries) really try to temper with the clock of the internet? Are we sure the won't succed and make all of us use it?

If consensus is only established by powerful AIs, the ones with the most powerful AIs are creating the truth.