Since Crimea is not a sovereign country, it shouldn’t be listed separately. You wouldn’t want to list Ukraine either because that would be an acknowledgement of an illegal entry.
I am almost completely sure that you’ve broken Ukrainian law, because you was on officially Ukrainian territory without crossing Ukrainian border. I suggest you to cross Crimean border from the Ukrainian side the next time. It’s doesn’t have to be a problem because Ukraine doesn’t require a visa from US citizens.
I think that you should include either Ukraine or Crimea as long as USA supports the fact that Crimea is a part of Ukraine.
I suppose US border agency does not require that you follow latest news from around the world, and then accept the recommended point of view on disputable matters. You did not cross de-facto Ukrainian border – you don’t list it.
Then you don’t need to tell whether Crimea belongs to Russian Federation or Ukraine: both consider it as their own part, so you just can let others decide which is right or wrong by specifying Crimea as a separate item on your list (if you wish).
Ultimately there is no penalty for writing the country name wrong on your Immigration form. The list is there to allow the immigration officer quickly determine if any secondary questions should be asked or to inform customs that perhaps a secondary inspection might be warranted (often used by Agriculture Department to route people for Ag Inspections).
Since Crimea currently is sort of a no man’s land when it comes to being officially recognized, I would just write down Crimea by itself. If the Immigration officer feels it should be written as Ukraine or something else, they will either change it for you or ask you to update the form.
They will likely be more concerned as to why you were in Crimea, rather than how you wrote it on your form.
USA, as most of the international community does not recognise Crimea as other than a division of Ukraine you should include Ukraine in your list, where Russia is presumably going to feature anyway if you have been living there.
You could simply list Russia(Crimea) as @gerrit had suggested but at the moment while not being recognized (by most) as part of Russia it’s immigration and border control is administered by Russia:
In March 2014, Russia occupied the Crimean Peninsula, which remains part of Ukraine notwithstanding Russia’s illegal military intervention. At this time the de facto Russian authorities are requiring that non-Russian citizens obtain a Russian visa to enter and exit Crimea by air, land, or sea.
So you won’t have Ukrainian border control stamp in your passport to show that you were in the country unless you have left or entered the penninsula by land.
Credit:stackoverflow.com‘