I think the question is more oriented around voting for the representation allotted to other states, rather than voting for candidates that will serve at the same level.
For instance, Presidents, Senators, and Representatives are all Federal positions. The states (or for President, the state's electors) get to pick their own representatives, though, and it would be odd for one state to elect another state's representatives to Federal office (e.g. a Massachusetts vote being counted in the Connecticut US Senate election.)
Likewise, all counties in a state vote in State elections, but don't vote in each others' county elections. This goes down the line to cities within counties, districts within cities, etc.
Not that I disagree with your point (it's totally valid to point out that elections from multiple areas can all serve in one body), but I think the question was more about citizens from outside a region voting for policies/representatives within that region.
President is a federal election, run by the individual states. Congressional members are likewise state run elections, but only affect the members assigned by each state. It's a nonsensical comparison.
They do. Residents of Massachusetts, Connecticut and other states all vote for President, Congressfolk and Senators.