I include USA because I have many cousins in Canada, Australia, and the UK and if they ever look at my work, I can't assume that they will know where anything in the U.S. is. For that matter, many of the town and county names in the U.S. are identical to overseas so I include USA to avoid any ambiguity. I've got ancestors in both Cambridge, Mass, USA and Cambridge, England for example.
My objective with place names is to be able to put a point on a modern map and find all of my ancestors that lived near there. I've been able to visit some of them and its really cool to walk through a village and know that I'm walking in the footsteps of my 18th century ancestors.
To do this, I need to use modern names but I want to save the old place names as a reference. My workaround to meet both objectives is to put the old name in the Description field and then use the modern equivalent in the place name field. For example, I've got many ancestors that lived and died in a town called Sawley in northern England. In the 17th and 18th century, it was in North west Yorkshire county and that's where it turns up in census. However they've moved the border and it is now part of Lancashire county. Just to add to the confusion, there's another Sawley in eastern Yorkshire which has many people with the same last name. This is one case where I use the modern county name as the place name. This allows any of the online mapping programs to find the correct place. I put the old county in the description field to remind myself to look in that county records when looking at old records.