Comment by umvi

Think of America more like 50 countries. Now take your school shooting example. A lot of states have made changes to their gun laws in response to this. Making federal (i.e. applies to all states) gun law changes is more challenging because you have to get 75% of the states on board with any constitutional changes. Without a constitutional amendment, any gun legislation ultimately must respect the existing 2nd Amendment so it's not possible to have Japan-esque policies without a constitutional amendment. Also USA takes up an entire continent so different regions of the us have different cultures and sentiment towards guns. People living in highly rural areas like Montana probably have favorable gun ownership sentiment. People living in highly urban areas like NYC usually have negative gun sentiment.