Actually, I think it is hard to do. What is difficult is foolproofing biometric security systems for access to buildings, computers, etc. But where the individual in question is always face to face with the person requiring them to put their iris/palm/skin cell on the screening device, it's pretty difficult to fake being someone else.
We can loose the records that contain our identity, and without being able to verify that identity we will be prevented access to our personal information, such as credit cards or employment. Biometrics can also be played. By that, I mean look at the credit reports. they are screwed constantly, but at least people understand that and do not hold them in high regard. Biometrics would be. No record, no identity. People could screw you in a heartbeat by deleting your record.
No, no, no! Your biometric database record would NOT be your identity -- it would only establish whether you are a citizen or non-citizen. Your presence in this database would have no effect on identifying yourself for purposes of credit, etc. No bank or credit-grantor is going to give you access to account #XYZ just because both you and the account holder of record are citizens -- they need to verify your identity, not your citizenship status. And as for people "screwing you in a heartbeat by deleting your record", they would have to 1) get hold of your biometric (let's say skin or hair cell) and 2) get access to the federal database, and 3) get access to the state database. No one could just get access to a database, and target someone for deletion, because there would be no identifying information attached to the database records.
Erasing an identity that is only supported by a biometric would be very dangerous and give the government the ability to control you.
That's why there needs to be a system of back-up databases at the state level. And no one's identity could be erased -- remember your identity wouldn't be in the database -- only the database record of your citizenship could conceivably be erased. But everyone would still be able to resort to the existing methods of proving citizenship in order to get re-entered into the database; i.e. presenting birth records, testimony of credible citizens who have known you for a long time, testimony of a current or former employer who has a record of having identified you as a citizen via the database at the time of hiring, etc. It could be a hassle, but no more than fixing an identity problem with the current credit reporting system, and much less damaging to your daily life, as there are relatively few things that one needs to establish citizenship for (getting a new job would be the biggest problem, but that already happens with incorrect negative credit reports). And how could the government control you? At worst, you could find yourself turned down for a new job or denied a security clearance at a government facility, due to inability to prove your citizenship, but that could be cleared up by the aforementioned legal process.
We do not need biometrics as we already know who is an alien.
How do we know who is an alien? Plenty of employers get tripped up by illegal aliens brandishing phony green cards, social security cards, etc.
Again, experience says not.
"Your biometric database record would NOT be your identity -- it would only establish whether you are a citizen or non-citizen. "
I don't think you understand your own statement. If you are not a citizen then your identity doesn't matter. You don't matter if you are not a citizen so who cares who you are. Not a citizen? No vote, no credit, not driver's license, etc.
"That's why there needs to be a system of back-up databases at the state level."
You obviously understand little about databases and government corruption.