In Japan, there are already multiple apps which use something like this to verify user's age via the "my number card" + the smartphone's NFC reader.

It's more or less impossible to forge without stealing the government's private keys, or infiltrating the government and issuing a fraudulent card.

Of course, the US isn't a functioning state, the people don't trust it with their identity and security and would rather simply give all their information to private companies instead.