Holding people accountable for crimes that other people have committed isn't workable and has no basis in law.
Actually there are 15 States that have Negligent storage laws for adults.
Texas,
California, Connecticut, Florida, Hawaii, Illinois, Iowa, Maryland,
Massachusetts, Minnesota, New Hampshire, New Jersey, North Carolina,
Rhode Island, and the District of Columbia.
Here is an example of the Penal code for the State of Texas.Other States have different penalties, some better some worse.
https://saputo.law/criminal-law/texas/weapons-crimes/making-a-firearm-accessible-to-a-child/
Here is Texas Penal Code ยง 46.13. Making a Firearm Accessible to a Child
https://codes.findlaw.com/tx/penal-code/penal-sect-46-13.html
If the child is under 17 and got access to a firearm owned by parents or any adult living in the same house as the child, and shot someone, the adult can be charged if he lives in any of the States above, between $500-$4,000 dollars plus One year in Jail-plus the person can be liable for a civil lawsuit personally that can run into the hundreds of thousands dollars.
If a child is 17 and over, he is considered an adult and is charged accordingly.
If a child from one of the States above, for example Texas shoots someone in the State of New Mexico that does not have these laws, the adult can still be charged criminally in his State and also be liable for a civil lawsuit. Here is a real life example;
https://www.nytimes.com/2018/05/21/us/parents-guns-negligent-storage-laws.html
Possessing a Gun in America is not as easy as the media would like people to believe. when I got my first gun they did a background check on me to see if I had any past criminal records of any kind including drunk driving. After that, I went to get my concealed license and the instructor had to see a current receipt of a proper gun storage device.
On top of that, even though federal law allows every citizen the Concealed Carry Reciprocity Act (HR 38), not all States honor that federal law and will put you in jail if you cross States with your license gun---- and their State does not allow the Reciprocity Act.
You can fight and win because federal law supersedes State law but it might cost you between 50k to 100k of fighting in court to prove them wrong.
So a citizen that is responsible and owns guns will learn all these laws to avoid jail and monetary punishment.
Responsible citizens have a saying. "For every bullet you shoot, there is a lawyer attached to it."
Unfortunately, there are tons of people over here that buy guns and within a year they go to jail for breaking a gun law that they did not know.
The video you posted has some truth in it. It's expensive to "Legally" own a gun. It's more expensive if you shoot someone.