If is a conjunction which should suggest possibility, but not absolute fact. Merriam Webster,com provides definitions, all of which relate to "possible".
Your first example:
For similar reasons fragile natural states cannot support many, if any, private elite organizations.
If any can be written possibly any
For similar reasons fragile natural states cannot support many, possibly any, private elite organizations.
The second example sentence:
As the two world wars and the Cold War of the twentieth century illustrate, external violence is a central if episodic aspect of the international environment.
may be abusive of the conjunction if.
The sentence probably should read:
As the two world wars and the Cold War of the twentieth century illustrate, external violence is a central, episodic aspect of the international environment.
In the first statement in the sentence
As the two world wars and the Cold War of the twentieth century illustrate,
the author establishes the episodic nature of 20th Century violence.
A conjunction might be used:
As the two world wars and the Cold War of the twentieth century illustrate, external violence is a central and episodic aspect of the international environment.
The use of if in this sentence probably should be classed as idiomatic. There may be other opinions on this matter; I'd prefer that if not confirm facts.