Post photo: world map | © Pixabay
Actually a matter of course and nowadays also a necessity.
The crew of Apollo 8 took the first photo of our world from space 50 years ago. It is the moment when people can see the "rising earth" [web page no longer available] with their own eyes for the first time and thus also become aware of its fragility.
On February 14, 1990, Voyager 1 captured the last image of our planet (“Pale Blue Dot’) and made it very clear that there is no substitute planet for humanity.
Anyone who still believes that they can escape from what is happening in our world on an “island”, no matter what size, will probably find it very difficult in the foreseeable future. There are plenty of indications of this: climate change, scarcity of resources, environmental destruction, pandemics, migration and last but not least wars that can hardly be delimited regionally.
With the former League of Nations and today's United Nations, bodies were already created to be able to meet all the challenges of humanity together. But since that time there have always been efforts by "diehards" and "flat-earners" to undermine and reverse these first steps towards solving the problem.
Since those days, however, there have always been people who see themselves as citizens of the world or cosmopolitans and who organize themselves in various groups. I don't want to go unmentioned World and European federalists who also make well-founded suggestions as to how our world can be preserved not just for one, but also for all the creatures on our planet for a very long time to come.
You can get an overview of these organizations on the World Citizenship website and, if you wish, you can “out” yourself as a citizen of the world.
Of course, I am also happy to answer any further questions you may have.
Addendum
On August 28, 2021 I repurposed my website worldcitizenship.com again. Now it is used to give me better access to other websites.
A little later I finally shut it down and just link to it.