It would depend on the specific machine. It is also possible that an American machine could be set up for 440v or 550v, so a general opinion really means very little.
Worst case, I suppose you could get a transformer on your end, to adapt from whatever to whatever voltage.
As for the change from 60hz to 50hz, I don't know of many instances where this could cause a problem except maybe electric wall clocks. However, you will get 20% less done in a day on 50hz
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)