1. The North did not "invade" the South - the South was still the territory of the United States since the elected government of the US did not recognize the South's "right to secede".
2. Japan did indeed invade China - and Korea, Mongolia, the Philippines, Indochina, Indonesia, and so on. Aggressors. Israel did not "invade the Sinai" - the Israelis seized the Sinai to stop Egypt from attacking Israel. Israel returned the Sinal after the peace deal was reached - that's called a "temporary occupation". The US did not "invade" Iraq. The US attacked Iraq to give the Iraqi people freedom from the despot running things. There are no additional states to add to our flag as yet.
3. In wars that run overlong, atrocities/violations of the laws of war will happen. During WWII, there were many incidents where US troops killed enemy soldiers and some were held accountable. In Korea, troops occasionally responded to the brutality of the enemy's handling of US prisoners by brutality themselves. In Vietnam there were likely some incidents of VC being thrown from helicopters and there is the undeniable crime of My Lai. The difference is that in none of our wars was this a policy of the US government and where it was proved, there were cases where the offenders were brought to justice. I served in Vietnam with the Marines and we treated civilians and prisoners with care and respect. My life was saved by one of my prisoners when I was badly wounded.
The difference is, that in WWI and other more recent wars, US policy, doctrine, and training emphasized humanity in our dealings with our enemies but as the wars grew longer, that humanity became less obvious. Our policy has not been seizing other countries to possess them - at least since the war with Spain - but to liberate them from other oppressors. The Germans had a belief in their racial and cultural superiority which gave rise to a vicious and inhuman set of policies that made them - and the Japanese - the enemies of all mankind. Look up Einsatzkommando.
P.S. - the Germans and the Japanese were well along with their own nuclear weapons and the aircraft/missiles to deliver them. We just beat all of them to the punch.
Israel did not "invade the Sinai" - the Israelis seized the Sinai to stop Egypt from attacking Israel. Israel returned the Sinal after the peace deal was reached - that's called a "temporary occupation".
Well, doesn't the same apply to Germany in WW I? The Germans "temporarily" passed through Belgium and "temporarily occupied" France because, well, once war was declared, the trenches had to be dug somewhere.
Either Germany could wait for France to "occupy" Germany, or Germany could "occupy" France. By your new definition, Germany did not "invade" France. It was a "temporary occupation" for the duration of the war.