What was the feudal system able to provide to the europeans after the fall of rome

As you would probably know, most of Europe was a part of the Roman Empire, apart from the modern day the Netherlands, Germany, Poland, Scotland, and Ireland (as well as a few eastern European countries). So, when the supreme power in Europe disappeared over the course of a few years, states that always relied on the Romans suddenly lost their leaders, and were vulnerable to the migrating of Eastern-Germanic tribes and therefore, were leaderless and defenseless. So, ambitious men created their own kingdoms and fiefdoms and promised protection to whoever would pay tax, provide arms, etc. That's the main reason for feudalism to appear all across Europe, in the aforementioned territories that were not a part of the Roman Empire, feudalism already existed (due to the disappearance of tribalism).  

The answer to this question is a

The american civil war