I doubt that the US would give up the dollar and I doubt that the Europeans would give up the euro, so no comment currency. At most they would discuss give the dollar and the euro price parity temporary, but I am not sure if that would work out well; it would involve artificially inflating dollar value or greatly devaluing the euro.
_________________________
In varietate concordia - EU motto
For small creatures such as we the vastness is bearable only through love.
- Carl Sagan