Europe, North Africa and Middle East are going quickly very unrecognislbe. Firstly this would mean Etruscan Italy, perhaps even unified Etruscan kingdom. Western Europe and Britannia remain Celtic, if not to this day at least much longer. Carthage is most powerful empire on Western Mediterranean. Not alternate Rome but still quiet strong. Eastern Mediterranean depends would there still be Alexander the Great. If so, Macedonia is strongest power in Balkans much longer but might still collapse to smaller kingdoms. Pharaotic Egypt is around much longer if not to this day. Ptolemaic Dynasty is going end in some point sooner or latter. Persia is much stronger.
And there wouldn't be Christianity so Europe would be Polytheist but much more diverged, Phoinician-Carthagian and Egyptian systems survive and Persia remain Zoroastrian.
So by 300 CE Europe, North Africa and Middle East are very different places. If Great Migration still occurs, Germanic tribes are facing very different cultures.