I'll preface this with the fact that I've heard absolutely nothing about this happening.
Yes, the electrical systems would need to be converted, and I know this was a major undertaking when the parade moved from Tokyo to Paris. I would have some concerns doing another electrical overhaul, depending on how the work was done the first time, and the type of phase controllers used within the units.
I'm sure that the floats could use a general sprucing up, and there's always the chance of damage occurring during trans-Atlantic shipping.
One final concern with this idea, and maybe I'm giving the average guest too much credit, but the parade tells essentially the same story was Fantasmic! While plenty of people would probably just see a sparkly parade and wouldn't necessarily be looking for a storyline, the Maleficent section would probably look familiar, and the princess floats in the third segment are very, very similar to Fantasmic's princess barges.