Well as far as i know it goes like this for the Danes and many other Scandinavian tribes in a nutshell:

First the robbed each other.

Then they decided this to be not cool any more and they robbed literally every other coast town in (mostly) Europe, so their known world. They took all valuables and the most beautiful women from them and sometimes even burned whole cities, just for the kicks.

Mongols did somewhat the same thing but mostly later in history. It's like https://en.wikipedia.org/wiki/Genghis_Khan copied these Norse guerilla tactics and implemented them on land with horses and bows somewhat. But in a much bigger scale.

Muslims "invented" religion as an "explanation" to conquer others. I don't get their desire to conquer deserts, but that is their cup of tea.

At least some of them interpreted the Quran in this way. And the moors just adopted this from my point of view.

But every of these cultures brought their culture and knowledge as trade off at least.

US-Americans can't bring their "culture" to others because nobody on the world these guys bomb wants it. Its even questionable if this lifestyle can be called culture.

Somehow you are looking the wrong way around at this i believe: You buy our stuff (at least professionals do), not we yours.

And since the people i'm the descendand from have over 1200 years of culture i simply don't need yours.

How hard can this really be to get, finally?