I have a sense that "every X is not Y" tends to be avoided by North American speakers. It has an archaic or "Britishy" ring to it, and the meaning is the same as a "not every X is Y".
For instance, here is a quote from The parliamentary register; or, History of the proceedings and debates of the Houses of Lords and Commons dated 1800:
Every man is not gifted with the candour and spirit of the learned gentleman; — does he think it a country for an honest man to live in?
Of course, this means "not every man is gifted ...".
Another very familiar example in the English-speaking culture is the adage:
All that glitters is not gold.
[Not all that glitters is gold: some things that glitter are not gold.]
The syntax of this saying right away alerts us that it is very old.
- not every X is Y clearly asserts: it is not true that for all X, X is Y.
- every X is not Y is either an archaic or British form which says the same thing as (1) or else a way of saying for all X, X is not Y.
- If the intended meaning is for all X, X is not Y, then the wording every X is not Y is a very awkward way to try to achieve that meaning, due to confusion with (2); a much clearer, more natural way to express this meaning is no X is Y.
For instance, a sentence like:
I tried to find a red marble in the jar, but, alas, every marble was not red.
is quite awkward, and better expressed like this:
I tried to find a red marble in the jar, but, alas, no marble was red.
Plus, of course, other possible endings: "there were no red marbles", "there was no such marble", and so on.
If there is some additional phrase or relative clause in "every X is not Y", then it can be acceptable. For instance "every marble that I looked at was not red". This wording tends to eliminate the ambiguity, and is more acceptable, though still inferior to "no marble that I looked at was red".