Seem is an infinitive (
things is its subject).
Making seem is a gerundial, object of the preposition
of. The prepositional phrase (
of making...are not) is an adjective postmodifying
tradition.
I really don't know why the author has chosen the adjective
architectural, unless it is being used metaphorically, but s/he is commenting on America's tendency to romanticize or idealize its heroes, traditions and practices-- making them seem more perfect than they are in reality-- or perhaps twisting them to suit their ideals. I cannot judge, for instance, whether this passage about Hopalong Cassidy merely refers to his sterling image as a cowboy, or rather to e.g. anti-Native-American sentiments in his films.
(I doubt, in any case, that America is alone in this very natural tendency.)