There would maybe, at best, be a shift away from the USD being the world reserve and having it become much like what we see in every other country but the USA. However that's unlikely any way you look at it.
Very difficult to say that government is hard to accept bitcoin, Many reasons are possible. I strongly agree with all the reasons you say. In my view because bitcoin is anonymous. And the government would probably have some problems, because bitcoin is used anonymously and no one knows for sure detail transactions, this resulted in the government can not take the income tax and other taxes that the government should have the right to be taken.