  Most stars form in highly clustered environments within molecular clouds, but
eventually disperse into the distributed stellar field population. Exactly how
the stellar distribution evolves from the embedded stage into gas-free
associations and (bound) clusters is poorly understood. We investigate the
long-term evolution of stars formed in the STARFORGE simulation suite -- a set
of radiation-magnetohydrodynamic simulations of star-forming turbulent clouds
that include all key stellar feedback processes inherent to star formation. We
use Nbody6++GPU to follow the evolution of the young stellar systems after gas
removal. We use HDBSCAN to define stellar groups and analyze the stellar
kinematics to identify the true bound star clusters. The conditions modeled by
the simulations, i.e., global cloud surface densities below 0.15 g cm$^{-2}$,,
star formation efficiencies below 15%, and gas expulsion timescales shorter
than a free fall time, primarily produce expanding stellar associations and
small clusters. The largest star clusters, which have $\sim$1000 bound members,
form in the densest and lowest velocity dispersion clouds, representing
$\sim$32 and 39% of the stars in the simulations, respectively. The cloud's
early dynamical state plays a significant role in setting the classical star
formation efficiency versus bound fraction relation. All stellar groups follow
a narrow mass-velocity dispersion power law relation at 10 Myr with a power law
index of 0.21. This correlation result in a distinct mass-size relationship for
bound clusters. We also provide valuable constraints on the gas dispersal
timescale during the star formation process and analyze the implications for
the formation of bound systems.
