Plymouth as the example (but his would be far from unique in this respect), as well as Canada (x2), Montserrat and Trinidad and Tobago here lists 21 USA states other than Massachusetts and also Wisconsin (x3) with a ‘Plymouth’, so adding country names would still not exclude all ambiguity. [plymouth-usa-wisconsin-sheboygan] would be ridiculous.
To my mind, fearing the OP will not to be adequately specific unless forced to choose a tag and/or others to be incapable of asking for clarification if necessary seems rather patronising. Yes, the first eight words of the Title of the Q referred to on their own would indeed be ambiguous, but it only takes reading one more word of the Title to achieve as much as [plymouth-uk] would. As far as I am aware “England” was in the Title right from the start. Might I make a plea for a little trust in the ability of Travel Answers users to take steps to provide clarity where disambiguation is appropriate?
At the moment [plymouth] is applied to a single Q and apart from [dubai] (38) and [berlin] (34) I have not noted any city tags (eg [bangkok], [boston], [brussels], [istanbul], [toronto], [vancouver]) with more than 30 Qs. Categorising down to a more specific location hardly seems required yet for searching purposes.