I would think that percentage would change if people knew what they were agreeing to. “Remove loopholes to get around background checks? Absolutely! Force private owners to report to the government who they sell a gun to, leading to a registry all all gun owners? Maybe not…”

Just curious, but have you ever purchased a firearm?

Background checks are standard procedure. I'm not sure what "loopholes" you are referring to. Usually this refers to private party sales. Do you want private party sales banned?

People often describe the fact that there isn't a background check for private sales in most US states as a loophole. Attempts to add such a requirement in some states, such as Washington have been clumsy and burdensome but it does seem like a good idea in principle.

Why do you think we don’t pass policy that >90% of people agree with? How do you propose to fix that problem?

(I’ll give you my personal opinion: we can’t because of structural flaws in the US political system, and the problem is impossible to fix.)