To be fair, we dealt with Germany through conventional warfare, but that "we" included the Soviet Union, and required millions of deaths on both sides.

America dealt with Germany in a conventional manner, and could have done so to Japan in a conventional manner. At the time America decided it would be expedient to use a brand new destructive device that the world has more or less collectively decided not to use in a first-strike capacity.

The intent in asking the question is why does the preceding commenter feel a war with China would look like an Afghanistan as opposed to a Germany?

Nuclear weapons and ICBMs to deliver them are the most obvious difference. The world in general is just so different than it was 70 years ago that it doesn't make sense to take the stance of "assume things are the same unless given an explicit reason not to" anymore.

My point is that a war with China would resemble a more traditional war as opposed to an insurgent conflict as in Iraq or Afghanistan. Why would we assume fighting a proper nation state would resemble fighting random lots of terrorists with varying agendas?

Your point falls through either way. A traditional full-out war is an improbability, because of any number reasons (balance of power between Russia/China/US, destructive capability of respective nuclear arsenals for MAD). With a proxy war more like recent conflicts (korean war, vietnam), a pyrrhic victory or an uncertain resolution is the most likely outcome. There's no point arguing who wins a global war in the 21st century because WW3 ends in irradiated hell on earth for all involved and would usher in the rise of whichever country was insignificant/uninvolved enough to avoid the ICBMs

You're assuming that what made the Iraq/Afghanistan invasions different from previous wars was the opponent rather than the advance of technology.

> You're assuming that what made the Iraq/Afghanistan invasions different from previous wars was the opponent

Is that not the case? What does technology have to do with these cases?

I would say the biggest effect is that modern media makes America much more sensitive to casualties, in contrast to the past where broadcast-style media like TV and newspapers were essentially hijacked for uncontested government propaganda. I'm sure if an expert thought about it for a while he/she would come up with more stuff around homemade explosives/IEDs, small arms, and the like, but I think media is the main one.