I have heard it both:
On someone's birthday –
God bless you
And also, when someone/thing is ruining up completely, we use the same greetings.
For instance, a newly appointed CEO is very badly known for his mismanagement. For a company called ABC, we then say,
God bless ABC
It clearly means that 'save ABC' from whatever is happening.
The question is how do we take god bless something if someone just utters it without any further comment/explanation. Because the greetings in many cases come as a standalone sentence.
The complexity doubles when you don't know the context. And, it can happen.
For example, if I'm getting migrated to a new country and some friend of mine living in the same country or having experience in visiting it greets – "Are you going to XYZ? Ah, 'God bless you!'"
My understanding:
When we use 'god bless' to an inanimate thing, it is generally negative and taunting. But then this is not true in case of 'God Bless America!'
The same thing is with 'All the best'. I've encountered many guys greeting 'all the best' in a sarcastic way. Say, a project in my company is completely ruined, and it is confirmed that the client has gone bananas due to several reasons. Now, if I'm replaced as the Project Manager has knows 'in and out' about the client and the project but has resigned from the company. He meets me for the final time and says, "Ah, you are on that project? All the best!' (chuckling!)
Best Answer
The phrases "God bless X" and "All the best" are nominally positive, but can be used in a sarcastic manner.
Context is everything when it comes to sarcasm, and sarcasm can be used on any nominally positive (or nominally negative) phrase. You may as well ask whether "I really love Minions" is positive or negative.
If there is no context, then there is no reason to assume that a phrase is meant sarcastically, and hence it should be taken at face value. For the examples this would mean that they are (almost certainly) being used positively.