There is an estimated (at least) 350,000 Catholic Masses celebrated every day on planet Earth. It is celebrated in every nook and cranny on the planet, by every race and nationality, and using every language. And each of these Masses is celebrated (generally) using the same scripture readings and the same prayers.
Every single one of these 350,000 Masses is actually doing exactly what Jesus said to do in scripture (Luke 22:19, 1 Cor 11:23-29) when he said “Do this in memory of me.” Catholics live that out as a Church over 350,000 times a day. That means there are 4 priests saying those precise words, “Do this in memory of me,” every single second of every single day.
Every one of these Masses is literally and continually making present Christ’s (once and for all) sacrifice on Calvary for all mankind. At any second you can join your own prayers to one. And we don’t only worship in union with those still living here on Earth, we are also joined by heaven’s saints and angels at every Mass.
When you participate in a Catholic Mass, you are participating in the same celebration as these other 350,000 daily Masses all over the world (you wanna talk about a “mega-church”?). We are all joined in the same readings and prayers and we partake of the same, specific Eucharist. And the rest of the time, when we are living out our faith outside of Mass, there are (literally) a billion other Catholics around the world continually offering it up on our behalf.
Now that’s unity (John 17:11). That’s communion.