Well, if we are counting TV series, my first was Green Hornet when I was 3 or 4 years old. That was in its original run, in '66 and '67. Though at the time Bruce Lee and martial arts left no impression on me whatsoever. And I remembered the Batman/Robin vs. Green Hornet/Kato episode.
The first American-made MA movie I saw in a theater was Norris's Good Guys Wear Black...well, that wasn't a MA movie. So maybe it was Circle of Iron.