Build service-area pages on county lines, because 'Nashville' means five things
Metro Nashville and Davidson County share one consolidated government while Williamson, Rutherford, Sumner and Wilson do not, and your site should show that you know the difference.
Someone living in Murfreesboro or Hendersonville does not think of themselves as living in Nashville. They still search that way, because the office they need is here. Both facts belong in your architecture.
In practice that means one substantial page per county you serve, written from the reader's side of the line: where you meet clients, whether you take appointments outside business hours, what the trip into town actually involves, and which matters you handle entirely by video.
Thin pages that swap a county name in and out get treated as what they are. A county page earns its place when it contains something only a firm practicing there would bother to write.
Immigration law is federal, so the county line does not change the statute. It changes the client, the drive, the money and the referral network, which is most of what a marketing page is for. Anything procedural about a specific court or agency office should be described carefully and flagged as worth confirming with that office or your own counsel.