The location of the 0 longitude line has less to do with the British colonial empire as such, and more to do with the fact that the British were the first people on Earth to invent a way of measuring longitude at sea accurately (John Harrison's famous marine chronometer). Of course these are ultimately related facts - the same package of technology that allowed the British to produce people like John Harrison who were capable of innovating a marine chronometer also allowed them to produce ocean-going ships that could conquer a global maritime colonial empire (and that had a use for marine chronometers).

There was in fact a rival 0 longitude line passing through Paris, France, that the French used for many years before standardizing on the British system; although this system would equally have resulted in the 0,0 point being somewhere in the ocean west of the African coast.

In an alternate reality, the prime meridian could have been chosen to pass through Florence, making 180° and the edges of the world map pass cleanly through the Bering Strait.

For a while, France had its own prime meridian with 0 degrees passing of course through Paris: https://en.wikipedia.org/wiki/Paris_meridian

Yeah, the prime meridian selection is the actually colonial part of the Mercator map. It's not like they were trying to make Europe look big, but they were trying to make London central.

https://en.wikipedia.org/wiki/Washington_meridians

  The Washington meridians are four meridians that were used as prime meridians in the United States which pass through Washington, D.C.