"John Smith III", etc. is not regarded with favor by many Americans. Not sure where this started; probably the practice of naming the first son after the father who was named after the grandfather, etc. When all three are living, it is a good shorthand way of referring to them.
Names like Earl "noble), of course, have no taint of royalty in America. Duke and Prince are popular names for dogs, but for people are mostly nicknames.

'Last names' used as first names are also common in Canada and Australia. Many of the old biblical names have disappeared and would be regarded as funny by the youth of today.

Finally, it should be noted that, in spite of the (mostly) common language, people of English (or even UK) ancestry are a minority in the United States. One should not expect names to follow UK practice.