It is found that the dynamics of spiral waves subjected to global feedback is extremely sensitive to the domain shape. Bifurcations in the velocity field which specifies the resonant drift of the spiral wave core induced by global feedback are analyzed. It is shown, for example, that smooth variation of the eccentricity of an elliptical domain induces a cascade of bifurcations that can dramatically change the spiral wave evolution. In a square domain a set of point attractors appears instead of the circular resonance attractor typical of a circular domain. These predictions are in good quantitative agreement with numerical integrations of an excitable reaction-diffusion system performed under global feedback.