What David Graeber's "Debt: The First 5000 Years" years has taught me, above all else, is that most economists from Adam Smith onwards know little about history and anthropology. I already knew that people like to spread just-so creation myths. In many cases, these end up being ungrounded in reality, but instead are meant as short-hand for the general culture belief of how something worked, rather than the reality.
A somewhat relevant example, look at http://westernreservepublicmedia.org/middleages/feud_peasant... as an example of how people tell untrue stories about the Middle Ages. The source is the Northeastern Educational Television of Ohio, and the page says "The main crops were corn, wheat, and beans. Near their homes, peasants had little gardens that contained ... tomatoes..."
In the US corn means maize -- "Indian corn". In the England "corn" refers to wheat, and in Scotland and Ireland it refers to oats. So either this is saying that maize (and tomatoes) somehow made it from the Americas to Europe before Columbus, or that the main crops were "wheat, wheat, and beans." Either way, it's wrong.
Here are more specific issues I have with your simplifications:
1) "The Feudal Era ... I specifically picked England, post-Reformation, after Henry the VIII."
The feudal era was already in decline by that point. Compare your statement to https://medieval-global-studies.wikispaces.com/Feudalism :
> At the end of the middle ages, feudalism still somewhat existed, but King Henry VIII gave the last blow. In the feudal pyramid, the pope was higher than the king. King Henry VIII broke away from the pope, and the feudal system had ended.
This is relevant because the Irish people believed that the Pope was the feudal head of Ireland, with Henry acting at the Pope's representative.
Or to http://karelma.com/english/history/henry-VIII.html :
> Thomas Wolsey ... was tirelessly ambitious, very quick-witted, and also ingratiating by aptitude, which appealed well to Henry VIII. Together they gave a strongly anti-feudal, reformist character to the politics.
Or to http://www.boydellandbrewer.com/content/docs/Decline%20of%20... :
> It follows that [feudalism's] disappearance [in England] between c.1300 and c.1500 changed medieval society fundamentally.
Or to http://www.sixwives.info/henry-viii-accomplishments.htm :
> King Henry VIII added Imperial concepts of Kingship to existing Feudal concepts
I cannot accept your use of a post-Henry VIII England as being representative of a feudal structure. By all accounts, feudalism was a minor part of Late Medieval England. I find it easier to believe that it's representative of a new and growing imperial structure, and an increasing centralization of power.
Compare England to Sweden, which did not have serfdom. The Swedish Empire was from 1611 to 1721. During that time, Sweden was one of the great powers of Europe. Your thesis would mean there are some intrinsically important differences between the absolute monarchy in England and the absolute monarchy in Sweden, because one was based on serfdom and the other was not.
Could you describe a few of the key differences between the hierarchies of the English and Swedish monarchies of the 1600s that were due to serfdom? Because I can't think of any, and your thesis requires that there be key differences.
2) "Allegiances in feudal societies tended to be very local ... why did all the soldiers follow Macbeth?"
This is, well, nonsense. Why did the soldiers follow Julius Caesar? Or for the same time period, look to Norway. Norway never had a feudal society. Why did all of the Christian, medieval, people of Norway follow their kings, even into battle?
Macbeth is nominally about Mac Bethad mac Findlaích, who died in 1057. Feudalism came to Scotland later, as part of the Davidian Revolution (see http://en.wikipedia.org/wiki/Davidian_Revolution ) during the reign of David I (1124–1153).
So not only are you using a fictional example to justify your views, but that fiction isn't even historically accurate.