The correct answer is...

your passport. Now those of you with passports will no doubtedly observe that the documents needed to get a passport are the very ones I debunked in an earlier post. True True but what is different is that a) someone at the state department, who is more expert than you or I, is looking at them, better able to discern their authenticity. Employers have no such requirement nor training. b) the government (that is We the People) declares you a citizen. Our constitution provides that our government can determine who is and who is not a citizen. We the people decide that. If you have a passport, you most certainly are a citizen. [there are some exceptions where a government can issue a passport to a non citizen but those are quite rare.]

No one is required to get a passport. In many countries their passport is their national ID. For Americans traveling abroad, it is your ID too. Lose it and you may be screwed. Immigrants and guest workers in the U.S. who enter legally are REQUIRED to have a passport. You are not. Hmm... so if you want to look like a U.S. citizen... ditch the passport. You do need your passport to re-enter the U.S. but once you are home, you can safely tuck it into a secure place. No one will ever ask for it in the U.S.

Since 9/11 there have been some attempts to create a national ID card. Ideally, this ID would be available and required of all citizens to get. Time and again, the polling suggests that the public is solidly opposed to a national ID card. People are concerned about big brother intrusion. As such, legislation has stalled. Fair enough... but recognize that a national ID would be something available to citizens and not to foreigners. So... you couldn't set up a requirement that says show a national ID or a work permit, in order to get a job. Instead our system now allows for immigrants to produce flawed, easily obtained, or forged documents that... well... everyone can have. Forget the work permit. Less is more.