I don't care so much about who did what, or how much americans were involved or not involved, I don't make a difference between italian and spanish productions, but I care for the style.
If an italian or spanish director made it, it's a Spag even if it lacks the typical style (but I would set apart the pre-Fistful westerns as forerunners), if someone from another nationality made it, the style decides it for me. And in most cases this decision is an easy one.
In China 9 is of course enough italian involvement to call it a SW, a close view at the credits shows that apart from Hellman and 3 actors all the participants were europeans, mainly italians.
The screenplay was written by Ennio de Concini, who is also named for idea/story.
But the director is an american, and he made this film in a way, which is not Spaghetti like, this film feels completely like an american western. And it was shot in english, not dubbed (or am I wrong? the dialogue doesn't sound like a dubbed one, is Testi dubbed?)
So the credits say italian, but the style says american. And the original title is, if you watch the credits, China 9, Liberty 37, not Amore, piombo e furore.
This film doesn't feel like a spag, so for me I would say it's none. It's a protestant western, not a catholic one. (to cite an interesting definition made in our forum)
giggle, defining time again