1-A aren't the first people from BNHA's Earth to arrive to Remnant
Gale is a little girl who is implied to be the cause of 1-A, Aizawa, and All Might suddenly being summoned to Remnant. She's too young to be using a Semblance... but she's at the age to show the first signs of having a Quirk. However, that would require that her having a Quirked ancestor. So, a likely possibility is that someone who had a Quirk that let them jump between worlds accidentally showed up in Remnant, and stayed long enough to have children, and Gale is their descendant, with her having a Quirk that mutates into allowing her to summon people from other worlds.Marcus Black is AFO's dimensional counterpart.
Marcus Black's Semblance has the same capacity as All For One's Quirk to steal his opponents' abilities and use them as his own.Salem will become interested in Izuku and Gale's skills.
After she receiving a report of what Izuku is capable of with One For All and Avatar Legacy, there is a chance that she will lose interest in the other Beacon students and instead choose to make Izuku just another subordinate to his insidious plans.Also, Gale's ability to summon people from another world with powers that operate outside the rules and limitations of Aura and magic, some with abilities that surpass the most powerful semblances known from Remnant would greatly capture her interest; She would probably try to manipulate her to use her power to his advantage like what happened with Overhaul and Eri.
The result of the fall of Beacon will be different from canon.
It is confirmed that the wyvern Grimm was petrified by the power of Ruby's silver eyes but was teleported along with the students of class 1-A back to Earth, which gives indications that many events that occurred in the canon were changed due to to the intervention of the MHA cast.The consequences of unlocking the aura of the students of class 1-A and the discovery of their semblance when they return to Earth.
If the existence of soul-based powers capable of being unlocked by anyone, whether they have a Quirk or not, becomes known, it would mean a great change in the paradigm and heroic society of MHA Earth. Also, the existence of otherworldly powers that operate outside the rules and limitations of the Quirks would attract enormous attention from All For One, the government and other factions on Earth.Remnant will develop technology that runs on alternative energy sources that do not depend on dust.
Due to the cultural and technological exchange that has occurred between the students of class 1-A and the inhabitants of Remmant regarding their scientific and technological advances such as satellites, spaceships and other alternative energy sources, Remmant will begin to change to not depend excessively on a single energy source that loses its power the moment it leaves the planet's atmosphere.An alliance between Salem and AFO to eliminate their enemies.
It is possible that both Salem and AFO will try to make an alliance to share their resources and information about their respective worlds to achieve their objectives, but each will try to betray the other the moment they stop being useful for their respective plans.The long-term effect of the fall of Beacon on both Remnant and the UA students.
Taking into account the division and mistrust generated in the canon timeline in the population on Remnant regarding the events that occurred during the fall of Beacon, this will affect any possible alliance between Remnant and Earth in the long term.Several Remnant characters will be teleported to Earth after the fall of Beacon but before the fall of Atlas.
There is a possibility that Gale teleports several of Remnant's key characters to Earth to ask for their support regarding the secret war occurring on Remnant.Class 1-A will return to Remnant when they recover
They're heroes, after all.