Do iPhones sold in the US support dual physical SIMs?
As it says right at the top of the support page you link to

In China mainland, Hong Kong, and Macao, iPhone 12, iPhone 12 Pro, iPhone 12 Pro Max, iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max, iPhone XS Max, and iPhone XR feature Dual SIM with two nano-SIM cards

iPhone 12 models sold in the US support one hardware nano SIM and one software-based eSIM though.