Re: "You cannot claim this city because you do not own some of the content

 - There are abandoned cities from players who may be from other countries or had a pre-order bonus or a different promotional item that unfortunately are just not obtainable. These include Country-specific special buildings, the Launch Arcology, Progressive Insurance, and a Crest promotion that ran for a limited time. I made a detailed list in this post if you're interested in the details.