If you used an abbreviation that is not correct for ANY state, the problem should be easily fixed. Supposing I had used ML for Maryland. I could use Tools menu > Global Search and Replace > select Places, Case Sensitive, Create Report of Changes. Use ", ML, USA" as the "Search for" term and ", MD, USA" as the "Replace with" term (leaving out the quotes in all cases). Check the Report of Changes, and all should be well.
On the other hand, if that abbreviation is correct for some entries and wrong for others, a global search-and-replace will just change some that are currently right, to make them wrong.
In this case, use a Custom List to search for the incorrect abbreviation. File menu > Print Reports > Custom > Select > Define > Any Place > Contains > (space+the abbreviation) > OK Put a check mark in Show Results Only > OK> Close Now each time you click on the binoculars or Ctrl+F, you will be presented with the list of people having that abbreviation in one or more placenames. This allows you to focus on changing the ones that need to be changed.
Or you can use Global Search and Replace: If the "Replace with" term IDENTICAL to the search term (except for adding a space at the end), the Report of Changes will give you a handy list of all occurrences of that particular abbreviation. Then you can replace the wrong ones, one by one.
Obviously, you will need to adjust the "Search for" and "Replace with" terms to match your database.