Throughout the ages, germany was terribly fragmented. Only unified in the 19 century and then split up again shortly thereafter. It probably has less time in being than the USA. Some German states were important, others not so much. Of them all, Prussia under Frederick is more deserving to be included. He was more important and influencial on the european political scene.
Oh, that I know. But, there is a bit of a distinction between the USA and Germany in this context. Germanic peoples have existed for well over a thousand years, and were a recognized type for a very, very long time. They were only unified into a nation quite recently, but they existed as different countries of a common ethnic background for a long time.
The US, by contrast, started as a British colony and became a country. Prior to that colony, and then that country existing, there was no American people in the sense that we think of Yanks today.
Germany represents all of those German peoples. Prussia just represents the Prussians, and in doing so, leaves out a big, and very influential, portion of Europe. I look at the inclusion of Germany as opposed to Prussia or Bavaria as a nod to the "civilization" of the German ethnic group, and not to a single political unity - and Germany is the obvious catchall to include those peoples.
Also, this isn't without precedent in Civ. Greece wasn't even close to unified at the times of its leaders, nor was India, among many others. They were put in as contemporary political units with the idea in mind, I think, to give a nod to the Greeks or Indians as an ethnic group, not as a unified political whole.
