Is it true that we no longer manufacture large transformers in the USA, and import ALL large generators such as go into dam power output?
Yes.
Here is the government report on Large Power Transformers (LPT). It gives the cost which will astound you, plus tell how long it takes to get one and tell you we are trying to start making them ourselves. Read page 6 and 7 for sure.
http://energy.gov/sites/prod/files/Large%20Power%20Transformer%20Study%20-%20June%202012_0.pdf