Admittedly, I didn't watch the 1 hour 32 minute video, but from skimming through it it seems to be mostly about the US and USSR. But natonalism has a meaning that is neither just patriotism or the type seen in far-right parties of the imperial core and Russia.

"Nationalism" initially means thinking that a group of people constitute a nation and should have self-determination. It is sometimes said to have come from the French revolution, as the French both used it at home as a uniting factor to replace the discarded authority of the king and keep holding the place together, but also as a dividing factor in wars abroad, as France was mostly fighting Austria through the Austrian netherlands (present day Belgium) and Austria's various vassals (multiple principalities along the Rhine plus the ltalian kingdoms). So when France occupied some place, anti-austrian grudges were fanned and independant "sister-republics" were formed. After Napoleon came into power, it was more kingdoms rather than republics, but the system more or less stayed, and after his final defeat, Austria got to claim a lot of territory back, but not everyone was happy to return to this.

In the following century, "nationalism" is more or less synonymous with "independantism", with sometimes also the idea of reuniting with people of the same "nation" living under a different "state" (eg Poles partitioned between the Prussian, Austrian and Russian empites). The Russian, Austrian and Ottoman empire, which both englobes many nations, were particularly threatened by the rise of Nationalism. The two later were broken after WW1, while the prior... Resolved its inner contadictions on a different way that I assume we're all familiar with.

Anyway, after that point, most nationalist movements in the global north are mostly "supra-nationalist": Their nation already has a self-determined state. But some think this state doesn't reflect their nation enough, either because there are too many people inside that don't belong to the nation (according to them) and sould be excluded, or because there is too much land that should "rightfully" be theirs but sits outside their official borders. This, combined with anti-communist reaction and the imperial boomerang bringing back home some of the methods invented to oppress the global south, leads to fascism.

BUT in many places, "nationalism" kept its original meaning as a people seeking self-determination. Irish nationalism, Puerto-Rican nationalism, Black Natonalism, and of course, many decolonial movements like in Algeria used this word. It's in this sense that Frantz Fanon wrote favorably of nationalism, which he sought was needed for African nations to get rid of the colonial yoke before they could build new ties.

I found a YouTube link in your comment. Here are links to the same video on alternative frontends that protect your privacy:

• yewtu.be
• inv.nadeko.net
• yt.artemislena.eu
• piped.video

Say what you will about its tenets, but at least it's an ethos