Haha. Nation building involves a boatload of money and the US post war policy was essentially to own the governments of the rebuilt nations. SK, JP are good examples of this and have modeled their development goals to mirror American way of life. From small things like TV shows (to non americans JPN and SK television is as obnoxious as US television with everything being over the top and colourful.) To much broader economic policy.
Be that as it may, the big countries generally dont fight each other because the losses on both sides will be massive but other than the US the other countries generally dont mess with smaller countries unless it has an immediate political outcome eg. Russia and ukraine.
Miltary history can teach all of us a lot but its inportant to take it with a shovel of salt. Victors write the books and rarely do they write about shortcomings. War is a terrible mess and almost entirely dependent on allies.
Lastly I would like to point out our naivete if we think a whole state will stand and wait for a belligerent nation to invade them in their father's ancestral land. The scars of war tend to fester. Should the big countries go to war, the outcome will not be anything like we hope or predict.