Spacetime isn't an object, like some sort of elastic jelly, that galaxies move through churning it up as they go. Spacetime is a mathematical object that we use for calculating observables in relativity. So there isn't any sense in which a singularity twists up spacetime.
The treatment of singularities is quite subtle in relativity. We describe spacetime as a combination of a manifold and a metric, where broadly speaking the manifold is what confers dimensionality and the metric is what defines distances. Singularities are not included in the metric, so in this sense the singularities are not part of our universe at all.
Note also that with one exception (the Big Bang) we expect all singularities to be hidden away behind event horizons so they cannot have any effect on us. This is known as the cosmic censorship hypothesis, and a singularity that wasn't behind a horizon would be a naked singularity.
Finally we should note that a black hole singularity takes an infinite time to form as measured on our clocks. This is one of the reasons for the suggestion that black holes don't really exist.