I don't think I can help you very much, but Elizabetha GERBER (nee Dohm) had two sons born 1823 and 1825. Although both of them ended up in Australia, they travelled to England from Germany. One of them married and had a family in England before immigrating. The other, my ancestor, came here in 1849.I visited the Records Office in Kew, London, some years ago and was lucky enough to find my ancestor's record on the ferry from Rotterdam to England in 1848.
Perhaps your ancestors went to the USA via England also? It may be an avenue for you to pursue.
I regret I can't help more. If you have any more questions please don't hesitate to get in touch with me.