In European countries, heraldry is highly regulated, as is its inheritance. Other than a few notable exceptions (Scotland being one), a coat of arms does not belong to a family, but instead to an individual. The rights to those arms usually pass to the first born son, who can use them undifferenced after the passing of his father, the original armiger.
In America, however, there are no official rules or laws governing the creation, use, or proliferation of heraldry. Basically, it's a free-for-all, and whether or not you register your arms with any of those private establishments in the original post, there's really nothing that you can do to prevent someone else from using your arms outside of copyrighting the specific image itself.
This lack of regulation, along with the general layman's knowledge that Coats of Arms were passed down, has given rise to the incorrect notion of "my family's coat of arms" and such like. Most of these so-called family crests tend to just be the individual arms of a certain person in their ancestry (and sometimes, someone of no relation who happens to share a surname), and laws in the country of origin may not give you any claim to them whatsoever. In scotland, there are blazons that are strictly linked to a surname, rather than an individual. However, they are still only used undifferenced by the head of the clan, while all descendants use a complex system of marks to show their relation to that person. And I believe in Scotland one must still be granted the use of arms by an official royal source before use, even if a relationship can be proven.
That being said, it's the US, so do whatever you want!
