3 There's no difference, although God Bless is more often used as a farewell greeting, and God bless you is more often used as an interjection, for example as a way of saying Thank you for a favour performed. In the same way, Bless you! is used, with exactly the same meaning, to express sympathy when someone sneezes.
What should the correct response be (from someone not overtly religious) if someone says "God bless" when parting company? "Bye now" or "Bye" doesn't seem an adequate response.
politeness - Response to "God Bless" when parting company - English ...
May God bless you. May God be pleased with you. May God accept your prayers. But why do we use "May" at the beginning of the sentence? Apparently, it doesn't make the sentence a question but more polite and respectful towards the God maybe? I cannot tell I heard this structure in any other sentence but religious ones.
2 By saying "God Bless America" you are indicating a desire that God will bless America in the future. You could even term this a prayer. "God blesses America" would be an indication that you think the blessing has already occured - or that the blessing is currently occuring.
1 You can also write God Bless America, the title of a song written by Irving Berlin and made famous by singer Kate Smith.
Personally I prefer "Gesundheit" to "God Bless you" because it satisfies the social mores regarding responding to a sneeze, and doesn't reference any religious traditions that may not be part of the sneezer's background. EDIT: Looks like Jimi said the same thing, so considerthis a confirmation.