As stated in many G2G, the drop down for the location fields is from Family Search.
When I removed the church from the Marriage Location, since it should not be in a location field, Baltimore, Maryland is seen in the drop down. United States is only seen with a year of 1776 -. There are other drop down choices that state Baltimore, Maryland with 1659-1776 or with Baltimore as county with 1674-1776, so the dropdown is correct, as it is.
People either choose the United States or they enter it, but the dropdown is correct.