Would a federal national ID actually do anything for presidential elections since they are ran by states, and states don't have to acknowledge the IDs if they don't want to (see sanctuary cities)?
Well obviously it was a thought experiment from a foreign point of view that, for the sake of the argument, supposes the USA is not a basket case.
But to repeat myself, if would probably be simpler and more impactful to make the customary Presidential election Tuesday an holiday.
Is a passport good enough for voter registration? or do you have to go through the get-id-to-get-id thing to get a state ID
In France ?
Passports are of equal "value" in justifying your identity as the National ID Card. Those are the two documents accepted as such. I think in some lower stakes situations (not voting though) you may use a driver's licence (Managed by the "Secure ID titles agency") or your Healthcare card (mandatory, universal, and free) since those now have an ID photo (that must follow official guidelines).
Voter registration is mandatory. You're automatically added if you turn 18 or after being naturalized.
If you change residence you need to ask to the town hall to re-assign you at your new address.
To justify registration at your new address you can use : An ID card or a passport OR a tax return, pay slip, ownership title OR a recent utility bill.
Town halls manage the voter rolls but the record is consolidated at the national level (Apparently by the INSEE, the national agency for statistics. In charge of the census too if I'm not mistaken).
When voting, you must present either an ID card or a passport alongside an electoral card (free and automatically mailed) which is stamped after casting the ballot. I'm not even sure the electoral card is mandatory, I was able to do without last time.
All paper ballots. Ballots are pre-printed for all options and at disposal at the station. No write-ins allowed (any added mark on a pre-printed ballot is nullified and discarded).
