Nick Mcbile wrote:

To the author: When are you going to tell us how did the Imperial
universe
diverged from ours? It's been 12 chapters already and we still don't
know
about that one. It's quite interesting given that most asian empires
were
not very expansionist. Maybe because they had China as a neighbour?
One
which didn't expand much either.

While I may not be the Auther, we were told in the first chapter.
Basically america lost the war for Independence from England so the USA
does not exist, thus did not have an effect on the world.

No.  That change would not have turned Japan into an expansionistic 
empire in the 18th century.