Are the white crystals on my American Cheese safe to eat? I have some American Cheese with fine white crystals on the outside of each slice. They have a gritty texture. Is this a sign that the cheese is spoiled, or just lactic acid salts like aged cheese gets?
It is calcium lactate crystals.  It is safe to eat.  On regular cheeses it is a sign that it is aged well.  For packaged, sliced american cheese I am not sure I would care for it.  But it is a matter of personal preference.