This American line currently begins with Ignatius Howard, born 1720-1725 St. Mary's City MD. (no doc for this yet but I am researching churches of the time for birth records). Many researchers have found no ancestry or family info for this man other than his descendants (see Kentucky Howard Lines). Family Tree Howard DNA shows that his haplogroup E-M35 (E1b1b1a1b1) (probably belongs to modern equivalent V13) is totally different than that of the Edmund Howard line (see FTDNA Howard Surname Project site).
FTDNA shows 4 other individuals who test E-M35 and may be related to Ignatius (sons/grandsons/nephews?) I will include docs on the haplogroup and its mutated subsequent lines such as E-V13 and V68. This is a very rare, interesting, and unique HG in England! I think Robert is one of his sons. Groves Leah Howard is also EM35, and he descends from the huge York county VA family of John Heyward and Margaret Clarke (online and in docs). So Ignatius is somehow related to that family though his name doesn't show up in the family tree.
I also found that there are early Howards listed in the MD Tax Lists 1721-1758 on the MD Gen. Soc. website. (See doc)
The doc provided on KY Howards has Revolutionary War record info for Ignatius and his wife Sarah (Sims) Howard. Also the doc on Ign Howard Notes.
All docs are under "media" tab.