The parent just explained why there is not much support from either the people or the politicians for a national ID in the US. Even if you don't agree with him, the assertion that "there is no reason US can't have a national ID card" is clearly false. Of course, an individual can obtain a passport if he wants, but that is only required to travel out of the country and only a small percentage of US citizens do that.

P.S. if you don't drive, your state probably offers a state ID card equivalent to the driver license. It is generally cheaper to obtain and replace.

There's no technical reason, but there are plenty of political ones. And since our government derives its power from the consent of the governed, if enough people don't want national IDs we won't have national IDs.