Holy crap, do you have no knowledge of history whatsoever?
Revolutionary war: Actually, it was the *colonists* getting high and mighty, deciding the king wasn't for them any more, and rebelling (becoming "insurgents", if you will). Britain tried to keep a hold on its own property, with the assistance of a large number of Americans, but failed.
Civil War: The South seceded, refusing to be part of America any more. Lincoln didn't like this, nor did much of the North. So, they fought to "keep the South", pretty much exactly like Britain had fought to keep northern America 70 years earlier. Slavery was the root cause of secession, but as it had existed for the previous 70 years, and would have continued into the future had the South NOT seceded, it was hardly about Slavery itself. Even the emancipation proclamation only freed the slaves in the states that rebelled.
World War II: Germany had little intention of invading the USA at any point, either then or in the future. It certainly never had the capability to launch a trans-Atlantic invasion, since it could barely manage a trans-Channel invasion against Britain (and once it invaded Russia, already a stupid second front, America was not even remotely likely to suffer an invasion by Germany within the next several decades). Japan had been increasingly militaristic throughout the 1930s, with its invasion of Manchuria in the early part of the decade, and then its invasion of China. The USA responded by issuing a trade embargo, and seizing all its American assets. Since Japan was almost totally reliant on US Oil, this was essentially an economic attack.
Japan was, at this point, sick of "meddling" by the Western powers, from the 1853 arrival of Commodore Perry, which humiliated Japan in forcing them to open up to the world, to the 1921 screwing of Japan through a naval agreement, where Japan was forced to have fewer large ships than the US or Britain, despite its assistance in WW1, through to it seeing the USA as meddling in Japan's sphere of influence in Asia by protesting against its annexation of various Asian states. The USA at this point was, of course, hardly innocent in the "taking territory from someone else" stakes.
Thus, in an effort to secure raw materials for themselves, since the USA would no longer supply it to them, Japan sought to remove the USA's influence from the Pacific, so it thought that a decisive assault of Pearl Harbor would so demoralise the USA that it would not retaliate, but instead leave Japan the Pacific.
Now, Japan was hardly a benevolent power doing only what it had to survive, since the trade embargo would not have come up had it not been so militaristic, but Japan *had* been screwed around by the Western Powers who saw it as inferior, and after its victories against Russia in the early 20th century, Japan thought this definitely not the case, and sought to establish its own Empire, the way the Western Powers had centuries earlier. It thought the Western Powers hypocritical in resisting ITS expansion, when they had done the very same thing.
You'll find that history is rarely black and white, with good and bad guys, despite what current politicians would have us believe.
