Point is, they don't need a national ID to pin you to some cell phone records that place you at location X at time Y, to get your CC usage data, to find out pretty much anything they like, to connect that to a license plate, to snag toll and other photo records of the vehicle from various sources, et c., and the only reason there are any restrictions whatsoever on that ability isn't because we don't have a national ID, but because we're not yet living under a tyranny. Difficulty IDing people isn't the limiting factor.
The public-private hybrid ID we have now is terrible and also carries all the same risks under tyranny as a national ID, which is at least not-terrible.
It's not like having a national ID would mean all the spying-data companies collect on us would automatically be shared with the government—more than it already is, anyway. It'd be the same as now, except with fewer ID-related problems for people.
The difference between rounding up people or not is often just whether it is logistically feasible. Right now, even if they collect every kind of data from every business, it would be a nightmare to attempt to collate it all, because it comes in so many sources with so many differing fields that may be out of date or inaccurate or wrong and would have to be normalized etc etc etc. Impractical to do on a very large scale. Except when there's a single identifier they could look for, which would completely solve the problem for them, and make it easy to round people up.
Companies that sell data to the government without the consent of the public is a huge problem we need to deal with, for obvious constitutional reasons (4th amendment).
What protects us from invasive search is not lack of a uniformly accessible system for identification - its due process. And if the government chooses to compel you against your will and without due process - whether or not you have a laminated ID in your pocket will be irrelevant.
A national ID would make the few cases where you need to hide your identity (like you're a 10 year old girl who was raped and needs an abortion, or the doctor that needs to perform it - https://www.seattletimes.com/nation-world/10-year-old-rape-v...) much harder. Until our government decides not to be so fucking crazy, we need to push back on its ability to unjustly track and then punish its citizens.