This article by Yasmin Moll, Assistant Professor of Anthropology at the University of Michigan, is pretty good and perhaps got lost in all the hubbub of the media circus around the Netflix series: Never mind Cleopatra – what about the forgotten queens of ancient Nubia? It is what Netflix should have done instead of throwing out what they knew was bait. In doing so, however, some good came out of it, as a lot of normies and people who don't know anything about history learned about Alexander and the Ptolemies for the first time, the Greek colonization of Egypt, and even arguments including Nubians of ancient Sudan. Most people living today don't form an immediate connection in their minds between Sudan and Egypt, despite the former being conquered and governed by the latter for much of the 19th and 20th centuries (in condominium joint rule with the UK after 1899, though).
I guess some Chinese conveniently ignore that Emperor Wu of Han actually had to fight Gojoseon in order to establish commanderies there, but the Goguryeo debate is the thing that's actually obnoxious, considering the Chinese hadn't really Sinified Manchuria at that point. Like other Korean kingdoms, Goguryeo had adopted Chinese customs and writing, but that didn't make them ethnically Han Chinese.
Nordics are Germanic, but not all Germanic people are Nordic, if that makes sense. The early medieval Christian Anglo-Saxons of Great Britain stood in rather stark contrast culturally from the repetitively invading Norsemen, but there was certainly a lot of crossbreeding among these groups and the native Celtic groups of the British Isles who had been previously Romanized to varying degrees. In either case, yes, the Germanic groups weren't terribly relevant to the Mediterranean until the Cimbrian War (113-101 BC). Later, in the mid-1st century BC they fought Celts and Romans in Gaul. After the Suebi king Ariovistus was bested by Julius Caesar, Germanic tribesmen became mercenaries and auxiliaries in the late Roman Republic in significant numbers, seeing service as far as Ptolemaic Egypt with the Gabiniani garrison there during the reigns of Ptolemy XII Auletes and our famous Cleopatra VII Philopator. That's probably the first time any Germanic people wound up in Egypt, though. Greeks didn't even exist in Egypt until the late 7th and early 6th centuries BC with the mercenaries and their families who were allowed to settle at Naukratis by the 26th dynasty. Persians weren't the first Indo-Europeans to live in Egypt, though, considering the Hittites. The first Celts in Egypt were probably the Galatians who served as Ptolemaic kleruchoi soldiers from the 3rd century BC onward.
For that matter, Germanic groups certainly didn't rule large sophisticated kingdoms in Europe and North Africa until late antiquity with the gradual collapse of the Western Roman Empire.
Barring civilizations like the Indus Valley Civilization who only had proto-writing or the Incas (who otherwise had impressive mathematics), use of the written word is often deemed a necessary marker for judging if a culture belongs to a civilization. Germanic peoples didn't even produce their own writing until the Elder Futhark alphabet of the late 1st/early 2nd century AD, based on the Latin model of the Romans, but used rather differently considering the religious function of runes. In the 2nd century BC Celtiberians in Spain were the first Celtic people to produce their own writing system, on either the Greek or Phoenician alphabetic models but was a semi-syllabary script like other Iberian ones from the 3rd and 4th centuries BC. Celts in Iberia and Gaul had also minted coins in Greek before Roman domination, and Balkan groups north of the Greeks such as Thracians, Illyrians, and Scythians simply used Greek whenever they produced writing. This is all pretty late to the game, though, considering Old Latin existed since roughly the 7th century BC (roughly contemporaneous with the Etruscan), after the Greek alphabet was fashioned from the Phoenician abjad in the 8th century BC. By the time the Mycenaean Greeks invented Linear B in the late Bronze Age circa 1400 BC, Egypt and Mesopotamia had already had writing systems for a couple thousand years. Hittites produced the first written Indo-European language a few centuries before the Mycenaeans.
In East Asia, there's no evidence of a writing system in China until the late Shang dynasty, with the Oracle bones dated to circa 1300-1200 BC, and shortly after that a more systematic and formulaic bronzeware script of the late Shang and early Zhou (11th century BC). The Chinese were thus a bit late to the game compared to the Hittites and Mycenaean Greeks, but were using writing on a widespread basis throughout the Greek Dark Ages. In South Asia, India is a really weird case, because it is clear they had some form of writing beforehand for passing down Vedic tales, but archaeologically there's not much evidence for written Brahmi scripts in Sanskrit until the 3rd century BC during the Mauryan period (for instance the edicts of Ashoka). Then there's suddenly a bunch of poetry and treatises on mathematics, astronomy, engineering, etc. It is clear enough, though, that Indians had used and adopted the Aramaic script beforehand under Persian influence.
You just went on Roma_Victrix's wild ride and tangent tour. Hope you enjoyed.