The phrase "the difficulty of identifying" is correct and usable in written English.
You can use it in any situation where you need to describe something that is challenging to identify or recognize. For example: "The difficulty of identifying counterfeit currency has led to an increase in counterfeit money circulation."
Such "off-target" effects greatly increase the difficulty of identifying the genes actually responsible for the selected phenotype.
The difficulty of identifying the killer, which popular folk lore would have terrorizing a local coastal community, is compounded by the biology of large sharks.
Another problem is the difficulty of identifying a growth stock.
Given the difficulty of identifying such offenders with certainty, the principle of incapacitation is controversial.
Officials refused to say whether or not the condition of the body contributed to the difficulty of identifying the man.
Ecological field studies are often hindered by the difficulty of identifying certain taxonomic groups.
The debate stems largely from the difficulty of identifying a disease based on the few medieval descriptions of the Black Death that have survived.
Part of the difficulty of identifying fake news is that the public and the media place so much trust in Twitter.
A major contributor to the difficulty of identifying and developing effective treatments, aside from delayed diagnosis, is the complex non-cell autonomous nature of the disease.
Biddle attributed the cause of the American stalemate in Afghanistan not to the difficulty of identifying national interests, but rather the means to achieve the ends.
Purchasers of the Philharmonic pass (nyphil.org) must contend with the maddening weaknesses of iTunes for classical-music lovers: the difficulty of identifying individual works in the iTunes library.
