  Important questions on the chemical composition of the neutral ISM in the
Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are still open.
It is usually assumed that their metallicity is uniform and equal to that
measured in hot stars and HII regions, but direct measurements on the neutral
ISM have not been performed until now. Deriving the metallicity from the
observed metal abundances is not straightforward because they also depend on
the depletion of metals into dust as well as nucleosynthesis effects such as
$\alpha$-element enhancement. We collect literature column densities of TiII,
NiII, CrII, FeII, MnII, SiII, CuII, MgII, SII, PII, ZnII, and OI in the neutral
ISM towards 32 and 22 hot stars in the LMC and SMC. We measure the metallicity,
dust depletion, and $\alpha$-element enhancements in the neutral ISM in the LMC
and SMC. We find $\alpha$-element enhancements in the neutral ISM in most
systems, on average 0.26 dex (0.35 dex) for the LMC (SMC), and Mn
under-abundance in the SMC (on average $-0.35$ dex). These are higher than for
stars at similar metallicities. The observed $\alpha$-element enhancements and
Mn under-abundance are likely due to bursts of star formation, more recently
than ~1 Gyr ago, that enriched the ISM from core-collapse supernovae. We find
total neutral ISM metallicities that are mostly consistent with hot stars
metallicity, on average [M/H]$_{\rm tot} = -0.33$ ($-0.83$), in the LMC (SMC).
In six systems, however, we find significantly lower metallicities, two out of
32 in the LMC (with ~16% solar) and four out of 22 in the SMC (3 and 10%
solar), two of which are in the outskirts of the SMC near the Magellanic
Bridge, a region known for having a lower metallicity. With the exception of
lines of sight towards the Magellanic Bridge, the neutral gas in the LMC and
SMC appears fairly well mixed in terms of metallicity. [abridged]
