How to justify capability for securing research funds in a faculty job application?
Selection committees know that there are different standards in different countries. What is important is that you give them a list of the grants you have obtained, along with a perspective on what that means in your country. In other words, document things such as the typical size of grants, the success rate of proposals, or maybe the typical amount of grant funding a professor at one of the better universities in your country has. All of this puts your achievements in context, and allows the selection committee to already get an idea how competitive you have been in securing grant funding and how that might translate to your competitiveness in the US.

If you make that hurdle, and the selection committee is still interested in your case, then there are sufficiently many international faculty in the United States that a committee can always call up someone who knows the system in your country and ask them what they thought of your track record regard research funding.