This is extremely useful information gathered from various sources by John Kaywood of Boulder, Colorado, USA, who is not an attorney.
You should not just rely on the advice that he has collated, but should consult a competent U.S. attorney of your choosing to seek legal advice and council on this subject; however, he should corroborate the details below as it is all a matter of public record.
“Completing a Legal Change of Name is the only method of affixing a title to a US citizen's name. It should be noted that the citizen must be very careful when using the new name, since the title can not be placed in the "title" field in official documents (where Mr. typically goes) since the individual doesn't technically have a title, they have a first name of "John" and a last name of "Smith of Glencoe" or somesuch.
Filing for, or attempting to prefix a legal name with a title that denotes privilege or peerage, such as "Lord John" or "Duke John" or even "Sir John" will, in most jurisdictions, be denied or be unlawful, since it creates a situation where the potential for fraudulent use is "prima facie" and thus violates one of the basic tenets of a name change, that it never be used for fraud.
Some states (New Mexico, for example) have no requirement for cause for filing of a name change. Simply filling out the proper forms and paying the court costs works. The majority, however, do have a requirement for cause, and some are rather strict in requiring a "compelling reason" for the change. According to some sources, often the most effective reason to use when requesting a name change is furtherance of one's career in the theater.
As for having the new name appear on official documents, the US Government does not, and will not, by law, officially recognize any titles, including those of royalty, nobility, peerage, academia, or otherwise, as part of a US citizen's name. No US citizen can formally request to have such titles added to an official US document. Presenting fully legitimate documents, even if signed by the Queen of England herself, will not get a title added to one's passport, according to one supervisor that I spoke with at the Bureau of Consular Affairs of the U.S. Department of State.
Each state differs on how it will handle a new name after having it legally changed to reflect a title. Most will simply place the name on official documents such as Driver's Licenses, exactly as an Order from a court of competent jurisdiction has shown the new name to appear. Thus, if you could convince the Court to make your name "John James Smith of Glencoe, Baron of Glencoe" then your license would most likely show a first name of "John", a middle of "James" and a last name of "Smith of Glencoe, Baron of Glencoe". It is fairly unthinkable that any jurisdiction with any sense would allow the license to read "Baron John James Smith of Glencoe" or somesuch, although catching an uninformed clerk at a local DMV office could yield almost any result.
To illustrate the sovereignty of the State governments, here is an example (with an alias to protect his privacy): A lifelong friend of mine is a judge at the County level in Texas, USA. Previously, he held the same position in Colorado. When in Colorado, the state placed an official designation on all official documentation regarding his
judgeship. Including his Driver's License, which showed him as "Hon. John Smith". When he moved to Texas to assume the judgeship there, the State refused to show any such designation on any documents.
This caused him a great deal of trouble, as over the course of the next two years he had to fight to get dozens of accounts, documents, credit cards, titles and other things "fixed" to remove his title. In one instance, he had a problem selling his vehicle because his name on the Colorado issued title didn't exactly match the name under which he was selling it. Moral of the story: Each state has complete authority with regard to how to, and whether to show any title on official documents, and it is often more hassle than it is worth to allow them to do so.
Credit cards and non-governmental issued ID cards, of course, will reflect any legal name change as it appears on an Order of almost any court, and in some cases may even amend the name to reflect the wishes of the consumer, since their goal is to make money, not argue over names. A problem can occur if the name on a credit card doesn't exactly match the name that appears in the credit databases (Experian and/or TRW), especially during online transactions where this information is routinely checked before even attempting to process a card. For this reason, it is best to have all documents match exactly the Court ordered name change format.
In summary, even "legally" becoming the Baron of Glencoe by purchasing the Barony doesn't change one's legal status in any way in the United States (nor most anywhere else other than, perhaps, Glencoe) and is not recognized as "official" in any manner by any jurisdiction here. While having documents in hand to show cause for your name change may help in some Courts, it is not a requirement, and does not automatically compel the Court to honor the name change.”