Depends which exoplanets you are talking about
The first exoplanets ever found - around a pulsar - were discovered by Americans at
the Arecibo Observatory in 1992. Granted they probably are not habitable worlds,
but neither was the one found around 51 Pegasi in 1995 by the Europeans.
Perhaps this explains why we haven't found ETI yet: Older cultures aren't as
adventurous any more and play things too cautiously.