You have to think about the problem the other way. The expansion of the universe and the background space is fundamental, and left over from the Big Bang. Within this expanding space, matter also acts under its own self-gravity and can 'decouple' from the expansion if the local gravitational collapse speed is higher than the local cosmological expansion rate in the same volume of space. A volume 2 megaparsecs across today has a differential cosmological expansion rate from center to edge of about 65 km/sec outwards, but if the galaxies inside this region produce a global escape velocity HIGHER than this, the region will be gravitationally bound against cosmological expansion. The same principle applies to larger and larger systems, however, eventually you reach systems that are so spread out, their average density is only slightly greater than the mean density of the universe, and are therefore only weakly bound against cosmological expansion. the limit passes to the scale of the horizon of the local visible universe, which has a mean density equal to the density of the universe, and exactly partakes of the cosmological expansion.