In the USA, manufacturers are on the hook for any failures, so proof is by company standard. There is no standardized proof in USA
Respectfully, and with no offense intended, this is inaccurate. In the US Proof standards are set jointly by the Sporting Arms and Ammunition Standards Institute (SAAMI) and the American National Standards Institute (ANSI). Copies of the manufacturing standards, including proof, are available from SAAMI for a fee.
If what you had intended was to write that proof is not legally required in the US, then that would have been correct. Proof testing in the US is voluntary. Here in the US we do not give our government the control over firearms common in Europe.
