The Diehm arms with gold/yellow chevron on a blue shield is the one most common at the family crest dealers these days. I've not found an authority for that version, but there must be one.
The Wertheim area is certainly within the region where the Diehms were found. My maps are not detailed enough to show Hohefeld. Lucky you have been able to trace them there.
The earliest Diehms in America seem to be: Peter Diehm & family of 4 show up on the 1790 census in Reading Boro, Berks, PA. Johannes Adam Diehm d 1802 in Fayette, Fayette, PA. Several Diehms age 64 & 65 were born in PA, so they were also here by 1794-5. By 1860 there were many Diehms (Deihms) in Lancaster, Berks & Philadelphia counties, PA (Pennsylvania Dutch = Deutsch = Germans); NY City, OH & IN. Most came from Baden (a state not a city, today called Baden-Württemberg), one from Baden-Baden (a city) and one from Hess Darmstadt (a duchy) [& location of Lauterbach, where the Diehms supposedly originated]. There are still many Diehms living in the Franconian area of Bavaria & in Baden-Württemberg. [Hope I didn't repeat myself!]
The tradition of my Diehm family says they came from Malterdingen (N of Freiburg). I have not been able to find the ship records for my family, but there are still Diehms living in Malterdingen, so it is a possibility. Jacob Frederic [Friedrich] Diehm & his brother John [Johann] Jacob Diehm came about 1857. The brothers came to Miami Co, Kansas in Apr 1857 from Illinois. Their parents: Sarah A. Diehm & L. [?] either came with them or later. Sarah A. Diehm's dates are: 14 Feb 1809-23 Jun 1889. I'm told, her husband L. died on the trip & was buried at sea. As far as I can tell, Sarah does not show up on any of the censuses. There is no subsequent L. Diehm in the family, so I wonder if L is a misprint for J = Jacob, part of both brother's name.