Since gravity curves space, I wonder how the locally increasing density of matter and energy due to the current galactic mergers with the Milky Way affects our perception of the universe.

Basically, if we have black holes coming closer to us, then the increasing curvature of space should make it look like the universe's expansion is accelerating, due to the increasing local gravitational red shift.

I'm sure I'm not the first to think of this but I wonder how well it's been studied, what the magnitude of that effect would be, and how we would even know if some dark matter were creating a dense gravitational field around the earth?