  Hollow-core anti-resonant fibers (HC-ARFs) have earned great attention in the
fiber optics community due to their remarkable light-guiding properties and
broad application spectrum. Particularly nested HC-ARFs have recently reached
competitiveness to standard fibers and even outperform them in certain
categories. Key to their success is a precisely fine-tuned geometry, which
inherently leaves optical characteristics highly susceptible to minimal
structural deviations. When fabricating fibers, these come into play and
manifest themselves in various imperfections to the geometry, ultimately
worsening the fiber performance. In this article, for the first time to the
best of our knowledge, these imperfections have been statistically modeled and
analyzed on their impact to the propagation loss in a Monte-Carlo fashioned
simulation. We have considered randomly varying outer and nested tube wall
thicknesses as well as random tube angle offsets. We found that the loss
increase due to perturbed tube angles dominates that of varying tube
thicknesses by approximately an order of magnitude for FM and two orders of
magnitude for HOM propagation at a wavelength of 1.55 $\mu$m. Moreover, the
higher-order-mode-extinction-ratio (HOMER) is proportional to the intensity of
structural variations, indicating an increase in the `single-modeness' of a
fabricated fiber. Furthermore, a bend condition worsens the loss contribution
of both effects applied jointly dramatically to a value of $+50\%$ at a bend
radius of 4 cm compared to $+5\%$ for a straight fiber. We believe that our
work helps to predict the performance of realistic HC-ARFs after fabrication.
