Internal wars and there relation to a states decline or unificatio

I have been following with interest the long debate about
Nagashino and found it fascinating to hear so many different
opinions. Then this sparked off a load of non Japanese related
history. Which is interesting as it shows how inter related all
history is.

I am interested in the warring states periods of china and
Japan, recently I read the romance of the three kingdoms which
highlights how destructive and the scale of warfare was at this
time. Mostly I
do read academic books like Friday, Farell, Owen, etc.

But Sometimes these books go so far into the detail of the
period I lose sight of the big picture, forgetting that as Japan was
involved in the Sengoku Jidai the rest of the world was forming it's
own bounderies.

This got me thinking of another question slightly off topic
but I am following the flow of this debate. The question is the
internal wars of Japan and China helped to form it's identity and
it's position in the world today, it was probably a very neccesary
thing. But my problem is theoretically how much stronger would Japan
have been without these internal wars?.

I mean the Kamakura shogunate was succesful but it had to
contend with Kublai Khan and Japan was not as well developed as it
was by say 1530. Can you imagine if the daimyo's all got on
(actually immposible) but if they all worked together it would be an
incredible power. If china was united throughout it's history too
what would that have done to the boundaries of the world today. I am
only theorizing but it is obvious that wars are part of human
society. But if those wars had only been external (invasions etc)
(like Hideyoshi Korea) I
wonder how much stronger the samurai as a class would have been.
Perhaps the Sengoku Jidai enabled Ieyasu to come to power and hold
it, but it also inevitably made Japan stronger but in contradiction
less able to deal with the Black ships when they arrived. I
certainly am not descrediting the Bushi just stating a point.

Anyone wanna comment. I have loads more research to do.
Thanks Mark