Gun ownership is much more tightly restricted in Japan and Brazil than here in the US.
Gun violence is much less common in Japan, and much more common in Brazil, than in the US.
Japan's population numbers about 126 million and is ethnically homogeneous. Brazil's population numbers about 208 million and is, like that in the US, ethnically diverse.
Gun-control advocates in the US argue that further restrictions on gun ownership will bring our level of gun violence nearer Japan's; gun-control opponents argue that further restrictions will bring our level of gun violence nearer Brazil's.
Our demographics are much more similar to Brazil's than to Japan's. That fact suggests to me that gun-control opponents have the stronger case.