I will come back to this point, because I happen to have visited the exact spot in Ciudad Hidalgo, where the hordes crossed the river, a month before it happened. So, when it happened, it was a bit of a shock to me:
https://www.elsoldemexico.com.mx/republica/sociedad/cientos-de-migrantes-cruzan-el-suchiate-hacia-mexico-hondurenos-guatemala-migracion-4724710.html/amp
This is the Suchiate river, between Guatemala and Mexico. It is not the Rio Grande, which is the border of the US (Texas) and Mexico.
These people tried to make their way through Mexico, a handful ended up in Tijuana, living in makeshift camps. Most never got into the US.
Some low information types were fooled by the initial images into thinking that an invasion was coming.