
most if not all the factions in BC where later enslaved by western colonial powers
Japan was too far to be invaded and both Korea and China may have acted as buffers - making Japan able to create modernizing reforms without objection or trickery from Europe or America.
colonial powers always need help from internal national rebels to enable them to infiltrate weakening regimes
- the internal political structures within japan were less understood by the colonial powers who were more interested in coveting the rich resources of Africa, south Asia and the south America.
japan had less resources and wasn't much of a catch by then - why conquer a land with less resources
(
Long Distances Open Sea Travel Attrition may have played a large part, probably 90 % - LOL
)