Earth X... casualties?

  In the classic JLA/JSA/Freedom Fighters first team up,  we learn from Uncle Sam that many of his comrades had perished in the ongoing battle against the feckin' Nazis.  This implies that the Blackhawks and Plastic Man had perished.  Of course, the 'hawks had been bought by DC and published through the 60s, even getting a superhero upgrade at one point, and Plastic Man had shown up here and there in various series as well.

I wonder if the Freedom Fighters ever ran into these pre-Crisis Earth 1 versions when they migrated from Earth X over to Earth 1 in their short lived series.  I always thought that was a mistake.  Leaving them on Earth X would have been way more fun and original, seeing them battle to restore their world from the Nazis.  But they didn't ask me, did they?

I used to have no problem keeping all these various Earths separate, knowing what heroes were where, but now, with all the alternate timelines and such, I find I don't even want to bother.