Most of the family changed their name to Magruder in the U.S. I do have many John Magruders in Prince George's County going back to the 1600s but I need more information such as date of birth, wifes name, parents names, etc. to help you.
You find MacGruder or McGruder mostly in Scotland.
Send me what you have and I will be glad to check it for you. firstname.lastname@example.org