Does airspeed affect the critical angle of attack on an airfoil?
Yes, through the Reynolds number

The Reynolds Number is a function of airspeed and is used to predict the transition from laminar to turbuluent flow: 

$$
{Re} = \frac{\rho v L}{\mu} = \frac{v L}{\nu}
$$

The critical angle of attack is affected by the separation of the boundary layer, which, in turn, depends on the laminar or turbulent qualities of said layer.

Do note that the Reynolds number of the layer is not the same as the Reynolds of the wing, although they are related.

EDIT: to visualize the efect, see for example the following graph (thanks @MikeY) 

Quite a bit of experimental work on low airspeed performance was done by Selig et al. at the UIUC, and their website maintains a significant catalogue of airfoil datapoints. 

Another resource worth checking is Airfoiltools,  which provides graphed Xfoil polars for an extensive seleciton of airfoils. Do keep in mind Xfoil´s prediction of flow separation points is numerical and therefore may not converge with reality at all points.