"Why won't you believe this study, you ammosexual?"

Because, like most of your 'proofs', it's bullshit.
Lankford’s study reported that over the 47 years there were 90 public mass shooters in the United States and 202 in the rest of world. Lankford hasn’t released his list of shootings or even the number of cases by country or year. We and others, both in academia and the media, have asked Lankford for his list, only to be declined. He has also declined to provide lists of the news sources and languages he used to compile his list of cases.
When someone refuses to release their data, it's because they're lying to you and don't want you to prove it.

Lankford cites a 2012 New York Police Department report which he claims is “nearly comprehensive in its coverage of recent decades.” He also says he supplemented the data and followed “the same data collection methodology employed by the NYPD.” But the NYPD report warns that its own researchers “limited [their] Internet searches to English-language sites, creating a strong sampling bias against international incidents,” and thus under-count foreign mass shootings.
That's some methodology to follow, isn't it?  Especially for someone claiming to honestly list crimes in other countries.

Lankford’s data grossly undercount foreign attacks(deliberately, I'd say). We found 1,423 attacks outside the United States. Looking at just a third of the time Lankford studied, we still found 15 times as many shooters.

Even when we use coding choices that are most charitable to Lankford, such as excluding any cases of insurgencies or battles over territory, his estimate of the US share of shooters falls from 31 percent to 1.43 percent. It also accounts for 2.1 percent of murders, and 2.88 percent of their attacks. All these are much less than the United States’ 4.6 percent share of the population.

One more dishonest study, pushed by the media because they don't care if it's accurate: it pushes the Preferred Narrative, and that's all that counts.