We don't make transformers in America. We get them from China and I don't think there are more than a couple in the country at any one time. China is not going to do anything to restore the American grid.
Page 33 for the high voltage medium sized unit facilities. Larger / higher voltage units are made by European facilities. Some U.S. facilities are considered sufficiently knowledgeable to produce large transformers; but, haven’t actually built any of the rail-car sized units to date.
Could likely operate transmission lines at a derated voltage / power capability, with the available locally sourced units.
https://energy.gov/sites/prod/files/Large%20Power%20Transformer%20Study%20-%20June%202012_0.pdf