I don't think it's true that Americans weren't saddened and concerned about victims in Beirut, but I do think part of the emotional response to the Paris attacks is that more Americans have read about Paris, studied the language in high school - college, listened to their music, viewed their art, traveled to France, etc---there's a connection for them.
It wasn't that long ago that Americans villified the French for not supporting America's invasion of Iraq.
"Freedom Fries", anyone?
My goodness how things change.