On the basis of data collected by a composite network of broad-band seismic stations, we investigated the relationship between the shear-velocity distribution and the parameters of shear-wave splitting in a stable continental region, testing the viability of the "anisotropic domains" hypothesis. We found that the region we examined - the northeastern US - is characterized by a surprisingly uniform anisotropic signature. While shear-wave splitting parameters vary with backazimuth at every station in our network, the pattern of this variation is very similar throughout the region. A simple one-dimensional model containing two layers with different anisotropic properties fits this pattern very well. We found that the isotropic shear velocity varies on a length scale of 100-200 km in this region, in contrast to the muted lateral variability in anisotropy. There appears to be little or no correlation between the ``rough'' structure in isotropic seismic velocity and the smoothly-varying anisotropic signature as evidenced by shear-wave splitting. We therefore conclude that in the northeastern US the concept of "anisotropic domains" - i.e. regions within the lithosphere characterized by coherent anisotropic properties caused by present or past deformation - does not apply.