It seems your professor is neglecting the influence of random chance. Just because an event occurs (eg. a state surviving or collapsing), doesn't mean that your (ie. in this example the leadership of the state) actions necessarily determined the outcome. People in general tend to search for reasons behind every outcome and that sometimes leads to people creating reasons for events that were just really random chance. We see this a lot in the media. For example, the idea behind evolution in the mind of the general populace is that all our different traits evolved based on natural selection, that all mutations that were beneficial were selected for and became the common form in the population, while the deleterious traits (and their underlying genes) were selected against and died out. This is in large part untrue, because it ignores the effects of genetic drift, where neutral or even mildly deleterious traits become the dominant (in a numerical not Mendelian sense) phenotype based on random chance, not any sort of selective advantage. A prime example here is the inability of humans to create vitamin C, which most other mammals are able to do, the original "ancient" gene our distant ancestor possessed allowed them to internally produce vitamin C, but a mutant loss-of function-allele arose that was ineffective and by random chance- ie. genetic drift- it became the dominant form of the allele in modern humans, because it was
not strongly selected against since humans lived in a vitamin C rich environment. This is why many neutral or even mildly deleterious traits have become the dominant traits in modern humans, even when they are not selected for. Selective pressure only is really decisive for strongly advantageous or disadvantageous traits (and remeber what is advantageous in one environment is not necessarily advantageous in another, so selective pressure will change as a species environment changes). For mildly advantageous or disadvantageous (which are the vast majority of phenotypic traits generated by mutation) traits genetic drift tends to outweigh selective pressure, meaning that whether a trait becomes the dominant form in the population or dies out is due mostly to random chance.
The point of this is that if random chance can dictate the evolution of our species it can certainly affect the course of nations, and it is naive to believe that our actions and our "rationality" alone decide our fate on either an individual or a societal level.
Besides your prof probably wont understand a word of anything I wrote anyway so he wont be able to disagree
PS: It gets even more interesting when you take into account genetic linkage, which occurs when you have two mutations on a similar of a chromosome (and thus resistant to the effects of crossing over during meiosis) that results in these two mutations staying together (and defying Mendelian style random assortment to be generally passed on together through multiple generations. When this occurs with a mildly deleterious mutation and a strong beneficial mutation, you can actually get a situation where selective pressure is pushing the deleterious mutation to become the dominant genotype in the population because it is piggy-backing with the strongly advantageous mutation.