i initially ignored the kind of racist narrative in the documentary i just posted, because it's sort of a standard roman narrative to call everybody else backwards and barbaric; if you've read any roman history at all, you're just sort of used to the irony and have developed a habit of shrugging it off. you see these kinds of skewed narratives in church histories, as well.
at the end of the day, i'd rather be free than "civilized". so, if you're going to line these things up against each other, i'll choose the roman concept of barbarism over the roman concept of civilization in a second. sorry.
but, what actually happened over the next several centuries is that the german tribes slowly caught up (in contrast to the celtic tribes, which were slaughtered and eliminated). these pro-roman histories that lament the conflict that followed from the successful defeats of imperial rome in northern and central europe forget to remind you that roman victories did not mean integration, but genocide. i mean, it was always the romans that showed up to fight and slaughter, not the other way around - at least at first. so, to argue that the german defense against roman imperialism led to hitler (which is a strange argument, given that hitler was a catholic that was aligned with italy against russia, primarily), and this is a horrible thing, is actually kind of similar to the sort of argument that the nazis made, you're just forgetting that the romans were, actually, pretty much identical to the nazis, in the first place (and what the nazis largely modeled themselves after).
so, if the romans had won, there might have been peace....at the expense of yet another genocide. just add it to the list, right? it's kind of a shitty way to look at it when you're really cognizant of the truth of it. i'd rather flip it over - if the romans had been wiped out sooner, we wouldn't have had to deal with a thousand years worth of empire, and the nazis wouldn't have had an empire to emulate.
but, the idea that the germans languished in backwardsness for the next 1000 years is completely wrong, and the only people that would honestly make that argument would be christians....and maybe muslims via christian sources, if they're so inclined to. as mentioned, what happened was that the germans caught up to the romans and eventually overtook and defeated them. this happened partly due to cultural diffusion, and largely due to the cultural decline in rome that took place after the adoption of christianity. but, it happened nonetheless.
these guys talk like 406 never happened, like rome was never sacked....
so, do i think these claims that charlemagne would not have existed if not for arminius are accurate? not at all. what was the first reich? the answer was the italo-german successor state of imperial rome, as started by charlemagne. charlemagne himself has overrun by vikings in a series of events that shadows the history. and, in the sense that there's a kernel of truth to it, that's not an alternate history with a happy ending - it's just an argument in favour of the widespread and frequent romanic genocides.