Larry, thank you for the honor.
If I changed a location name to United States, it was because that was what is in the drop down box for locations. Not because USA is incorrect. Usually, I'm adding the county information and using the drop down list, so I'm getting the county information and United States comes along for the ride.
Please feel free to use USA -- which is completely acceptable on WikiTree. I'm sorry if I changed that on a profile that was after July 4, 1776. As part of the Clean-A-Thon at the end of April, most of the USA too early in birth, death and marriage locations were removed. WikiTree rules are to use the location that was used at the time, so United States of America (or United States or USA) are not used in a location before the Declaration of Independence date.