What if someone in the German government has enough sense to realize that trying to get Mexico to commit suicide for the greater glory of Germany is a non-starter and the note is never sent?
I think - unless you change also German military orders to no unrestricted submarine warfare - the outcome of the war would be not so much different. The US may get into war at a somewhat later date but the unrestricted submarine warfare gave them casus belli galore. It is only a matter of time.
What if someone in the German government has enough sense to realize that trying to get Mexico to commit suicide for the greater glory of Germany is a non-starter and the note is never sent?
Fah! If the Germans didn't send it, the British would have!
Remember all those Belgian babies being slaughtered and those Belgian nuns being raped?