alternatehistory.com

With any POD starting at 1788 (the ratification of the US Constitution) have, by the 21st Century, a majority of the world's nations, including most of the Americas and Europe, have the right to own and bear firearms be protected by law, similarly to the 2nd Amendment, and have gun ownership be as widespread as it is in the current United States (few to no restrictions on what firearms are legal to own, right to concealed and open carry, laws protecting the right to self-defense). The existence of gun control movements and parties is acceptable, but the right to bear arms should be a major topic of political discussion worldwide.
As a bonus challenge, have a sizeable minority of the world's nations (25%-ish) have gun laws as unrestrictive as the most pro-gun states in the US (Arizona, Alaska).
Top