If I read Weber correctly, the differentia specifica of European capitalism was good luck - right place and right time - which allowed the bourgeoisie gain an economically dominant position. Political/cultural institutions (including rationalism and bureaucracy) were merely "elective affinities" of that economically dominant class position - that is - they were instrumental in legitimating the ascent of the bourgeoisie. Their cultural monopoly is owed to the economic monopoly of the class that espoused them, ex post facto rationalizations notwithstanding. I think that Weber's "Protestant Ethics" and Marx's "18th brummaire" carry esentially the same message, they differ only in emphasis.
The fact of the matter is that bureaucracy was developed earlier in China - but because of a few strategic mistakes / bad luck that stymied the expansion of the Chinese empire - today we talk about "European rationalism" rather than "Chinese rationalism."
Civilisational development is like a football game - those who get the best seats are those who arrive first, not necessarily those who are the smartest or best organized. There are instances when the smart/well organized people get pretty bad seats because they arrive late due to their other committments.
Also, I do not think that Amerikkkan infatuation with guns has its roots in the nature of capitalism. It would be too noble. We should rather seek its roots in the fact that the New World was originally no more than a penal colony - a dumping ground for criminals and assorted undesirables. The culture of violence they brought with them evenetually sublimed to the 'god-given' right to bear arms - which is a wet dream of every criminal.
Further proof comes from counter-evidence of religious fanatics who programmatically renounced violence - states and places dominated by these type of immigrants (cf. New England, or Amish villages in PA) tend to have much more negative attitudes toward guns.