Of course, mass shootings and murders are unacceptable, shouldn't exist at all and its practice must be heavily fought back by every socities. The point is that there are nations much more dangerous to live than USA, which usually the media doesn't talk about, because it's more interesting to focus in USA, since there is an anti-gun agenda to push forward. There is also another detail to pay attention to regards tyranical countries where informations aren't clear, legit and open, so it's hard to measure their real numbers for real.
https://www.datapandas.org/ranking/murder-rate-by-country
Are you sure El Salvador is within the Top 3 of the ranking about rate of murder/criminality worldwide? Because from the impressions I have gotten from Bukele's crackdown against organized and gang crime, it would seem the rate of criminality in that country has decreased significantly (or at least that is what I have heard on the news). Anyways, keeping that to one side, I totally understand why the news from the United States and related to guns are easier to find and quickly picked up by the media, when compared to the news of violence goin on in other countries. The USA is the political center of the planet (whether we like it or not) and one of the few countries where people has the explicit right to arm themselves, so there is more relevance to talk about violence happening there than violence happening abroad.
Some unfortunate happening going on in other countries would need to be specially deadly to make it to the news, as in the case of the horrible terrotist attack which took place in Russia yesterday.
Also, perhaps it is not all about a lobby or coordinated effort to get rid of the Americans to carry guns around, but the voices of people who have lost family members in mass shootings who are not longer willing to live in a society where violence is becoming normalized.