Most alien invasion movies deal with the central idea in H.G. Wells' The War of the Worlds, a radical change in perspective. His Martians look upon us as we might look at microbes through a microscope. Humans are made to face the question of what our cumulative history (moral, social, etc.) amounts to in the presence of a superior, celestial other. Wells suggests there's hope for us, that we're not so insignificant, by having the Martians taken down by bacteria, which were no more significant to us than we were to the invaders. As it turned out, we should've had more respect for bacteria.
An optimistic response to our diminished ontological status would be Gene Roddenberry's Star Trek universe, where Earthlings get over their petty (in the cosmological sense) differences to work together in establishing our species' significance in an ever expanding world. The success of Earthlings in the Federation is because liberal humanism is taken to be an absolute, superior to all the alien moral alternatives found in the universe (Vulcans might be our intellectual superiors, but they don't possess our heart and good old common sense). The wish fulfilled here is that humans overcome all our cultural, socially constructed differences to prove the importance of what unites us, presumedly biology and whatever inalienable rights obtain therefrom (again, liberal humanism).
The more pessimistic spin is seen in Robert Wise's The Day the Earth Stood Still, which involves a representative, Klaatu, from a council of master races (not unlike the Federation) coming to Earth with a warning: do what you want to each other, but should you try any of that human-all-too-human bullshit with us as you travel into space, we have the technology to annihilate you. If we're to be united, it'll be through negation, all of us being fundamentally different from the other, causing us to cuddle together in fear. A similar togetherness led Earth to attack the bug planet in Paul Verhoeven's Starship Troopers, the bugs not possessing the technological power of Klaatu.
Even more cynical is Neill Blompkamp's District 9 that suggests if there is a unifying human instinct, it's bigotry. The alien arrival doesn't fundamentally alter class and racial divisions, but instead proves shit rolls down hill. The aliens are restricted to the poorest area where they're subjected to discrimination from the most discriminated of humans. Although biological alteration of the protagonist results in his empathizing with the alien plight, it's not biology per se that's the basis for moral insight (as it is in Star Trek), but rather being socially reconstituted as other in the eyes of his (formerly) fellow humans, particularly those from his bourgeois background.
Gareth Edwards' Monsters applies a similar socio-historical determination to extraterrestrial reception as District 9, where the invaders aren't seen as transcendent beings that defy our categories, but are instead reduced to extant concepts of class, nation-state boundaries and otherness. The octopoid aliens (a cross between those in The War of the Worlds and Watchmen) are quarantined in Mexico along with the majority of Mexicans. Fulfilling the Minuteman Project, there's a Great Wall now separating Central from North America. Regardless of the terror and destruction being inflicted on the resident population by the giant octopuses, the only immigrants allowed into the States are the wealthy. An interesting enough premise, but nothing much is made of it except as backstory for yet another bourgeois coupling.
Basically, all the suffering exists so that the two protagonists can find time to fall for each other. Andrew, a jaded photojournalist (you know he's jaded because he prefers to take pictures of dead, indigent children that'll make him more money than those of the still living), is forced to return Sam, his boss's daughter, back to the safety of the States. Mostly the film is a lot mumblecore-styled cooing behavior against background ruins, occasionally punctuated (and only very occasionally) by the appearance of a monster killing some Mexicans or being bombed by American jets overhead. It's not until Andrew and Sam witness two octopuses making out that they fully realize love is the only way out of all this destruction, the only thing that connects us all. That is, provided you're not poor or an alien who accidentally landed on the wrong planet. As the Christians would have it, some have to suffer for the rest of us to be saved.