Though I personally don't care for the sound of
Earl, it seems perfectly acceptable as a name to me.
I really don't think anyone in the USA thinks of the title when naming a child
Earl. It has been established as a regular given name in the USA for so long that Americans think of it primarily as a first name and certainly don't perceive themselves as using the name because it was a title. Though people in the UK may think of the title when seeing or hearing something like "
Earl Rochester", an American would automatically assume this is someone's name. You have to put the "of" in (
Earl of Rochester) before Americans would think of it as a title.
Earl,
Duke,
Queen, and
King are all also English surnames, and probably as much or more of the original motivation for using them as given names in the USA comes from that. I think many of those who name sons
King in the USA these days are honoring
Martin Luther King, Jr.