WARNING: The following contains major spoilers for Men in Black: International, in theaters now.
The original Men in Black firmly established the history of the agency, which polices aliens living in secret on Earth, and protects the planet from intergalactic threats. But the fourth film in the franchise, director F. Gary Gray's Men in Black: International, not only explores that backstory, but gives it a massive makeover.
The 1997 original revealed the organization's origin is rooted in mid-1950s America. As Tommy Lee Jones' Agent K explained to Will Smith's Agent J, the Men in Black began as a small government body tasked with making first contact with aliens, and finally succeeded with refugees on March 2, 1961. K was part of that group, only because he got lost while trying to deliver flowers to his then-girlfriend. And, so, he was recruited, with the agency transitioning from a joke into one of the country's most important organizations.
It was decided Earth would become an apolitical zone for aliens without a home, and the agency broke away from the U.S. government to become the Men in Black. The founders believed autonomy, and the ability to work in the shadows, would be the best way to protect Earthlings while providing a haven for aliens. The founders of the agency were the seven agents present at the site of first contact, an amateur astronomer and the man who would become K.
However, in Men in Black: International, the idea of Earth providing a home to extraterrestrial immigrants is revealed to have begun long before -- in the 1800s, to be a little more specific -- thanks to Charles Eiffel and his Eiffel Tower.
When Tessa Thompson's Agent M comes to London to work with H (Chris Hemsworth) and his boss, High T (Liam Neeson), to recover a gun that can destroy planets, they clue her in on this history. Through photographs in T's office, we see that Eiffel actually built the tower in Paris to double as a scientific base. Disguised as a civil engineer, he created technology that opened wormholes, allowing alien refugees to come to Earth. That means first contact was actually made around 1889, and that Europe was the original border, not New York, as we previously thought. Eiffel accommodated the refugees, disguised them, and seeded them across Europe, where they tried to eke out a better life.
This isn't necessarily retcon, per se, because it could mean that only the U.S. branch was established in the 1950s. The London office of Men in Black recognizes Eiffel as the official founder, so it might well mean the Americans were behind the times, and followed suit seven decades or so later. In any case, Eiffel didn't don a black suit, and we don't see any agents working with him in the 19th century, so it stands to reason he proposed the idea of Earth taking in aliens, which then led to the creation of the Men in Black.
The film doesn't provide any insight into the other chapters apart from New York and London, but High T makes it clear the initiative didn't start with America and certainly won't end there. As for the prominence of the Eiffel Tower: That's where the Hive try to invade Earth in the beginning of Men in Black: International, and H later states that Paris has indeed become famous across the galaxy for aliens seeking a new way of life. That makes the Eiffel Tower more than simply a landmark.
In theaters nationwide, director F. Gary Gray's Men in Black: International stars Chris Hemsworth, Tessa Thompson, Rebecca Ferguson, Kumail Nanjiani, Rafe Spall, Laurent Bourgeois, and Larry Bourgeois, with Emma Thompson and Liam Neeson.