From: Somerset, U.K.
Yes, Manhattan and Washington are the sisters, and constructed about seven years before America. With those distinctive funnels, America bore a greater resemblance to the last Blue Riband holder, United States, though constructed about 14 years earlier. That forward funnel was, in fact, a dummy.
The two sisters ended up in the mothball fleet on the Hudson River from (?) about 1952, whilst America remained on the Transatlantic run until 1963. The story of her subsequent decline and stranding off Fuerteventura makes sad reading. Not long ago you could make out the wreck on Google Earth, but her destruction by the sea has proceeded so far that this may no longer be possible.
Things seem to have looked up a bit for 'Big U' at Philadelphia in the last twelve months.