Three things seem to me to be possibly explanations
(1) That Germany deliberately provoked neutrals in order to have all the world against her & then to withdraw from the unequal task.
Im afraid this is too fanciful a dream to hope for its truth
(2) That Germany on the head of Wilsons stand for peace thought she could do almost anything without provoking war.
(3) That Germany judged that the only possible victory lay in hampering Englands freedom of commerce and that the gain to her in this outweighs the disadvantage of having USA to reckon with as an Enemy