  We measured the cross section of coherent elastic neutrino-nucleus scattering
(\cevns{}) using a CsI[Na] scintillating crystal in a high flux of neutrinos
produced at the Spallation Neutron Source (SNS) at Oak Ridge National
Laboratory. New data collected before detector decommissioning has more than
doubled the dataset since the first observation of \cevns{}, achieved with this
detector. Systematic uncertainties have also been reduced with an updated
quenching model, allowing for improved precision. With these analysis
improvements, the COHERENT collaboration determined the cross section to be
$(165^{+30}_{-25})\times10^{-40}$~cm$^2$, consistent with the standard model,
giving the most precise measurement of \cevns{} yet. The timing structure of
the neutrino beam has been exploited to compare the \cevns{} cross section from
scattering of different neutrino flavors. This result places leading
constraints on neutrino non-standard interactions while testing lepton flavor
universality and measures the weak mixing angle as
$\sin^2\theta_{W}=0.220^{+0.028}_{-0.026}$ at $Q^2\approx(50\text{ MeV})^2$
