Further to what Dale said below and to RJ's wicked good sense of humor? People from the US are made up of so many different areas of the world that there is no truly US DNA. We all come from somewhere else as far as the DNA Goes.
You might want to checkout the GenoGraphic Project from National Geographic for more information about our origins. Mags
Login to your myFTDNA account at Family Tree DNA. At the bottom of your mtDNA Matches page is a button linking to Upload to MitoSearch. Click it and add your e-mail, earliest known ancestor, link to your ancestry in WikiTree, etc. Then click save.
If you get an error message when saving then don't try to upload to MitoSearch ID again. Instead go to
www.mitosearch.org/search_start.asp?providerkey=542060
and if you uploaded and saved to MitoSearch then you should now be able to see your MitoSearch ID.