Popular culture has a standard definition. It is the arts that appeal to the largest audience, is not innovative, does not raise questions about the accepted norms, and contains anticipated elements (individuals can anticipate what comes next or what the moral is to be, etc). Popular culture is widely disseminated through mass media and is the total collection of all the perceptions, beliefs, ideas, and attitudes of mass society. So your question is asking: How did Griffith impact the general mass culture disseminated to the widest public audience through mass media, i.e., film and, later, television?
The greatest impact on popular culture is Griffith's innovative film techniques. The film techniques he created are still of great importance today in film and in television. Close-ups were Griffith's brain child. He employed medium shots (shoulders to head) and close-ups (head only) and even extreme close-ups (one feature, like lips) in his films to record actors' emotions and create empathy.
Another is dissolves and fades. Griffith's contributions include wipe-fades, overlapping dissolves, and decreasing cameo dissolves. These are still used, even the cameo dissolve with its blackened edges that gradually fades to a smaller and smaller circle of vision. True, this one has become a cliché used mostly for ironic humorous effect, nonetheless, it is still in use.
One of his greatest contributions is in editing. He innovated rapid, short cuts of film that cut from one action or character to another in rapid succession (we are so familiar with this popular culture technique now, it is taken for granted and barely noticed). This cross-cutting technique builds tension and creates suspense while giving a heightened sense of action.
Griffith also innovated the contemporary relationship of the actor to the camera. Through his emotion revealing close-ups, he created a role for the camera as a witness, something very different from the capabilities of the proscenium arch of the theater. In addition, because of his cross-cutting technique, the camera took on a omniscient role of being the impartial--or partial--observer at multiple events. For instance, the camera can observe the escape of the pursued girl, the dashing rescue attempts of the hero, and the recapture efforts of the villains.
The personal "eye" of the camera--either objective or subjective--is a critical part of popular culture film and television productions today. An example of a participatory camera in a contemporary film is in Mama Mia! (2008) when Donna encounters Sophy's "three dads" in her "old goat house." When the men are giving their excuses for being there, a hand-held camera spins around from one character to the next registering their actions and reactions as an invisible participant in the scene.
The close-ups and this personal camera required and affected a change in acting technique. The large emotive displays of the theatrical stage had to give way to intimate expressions and subtle emotions that the sensitive presence of the camera picked up in keen detail--acting as we know it today. In addition, Griffith began the very popular popular culture practice of adapting short stories and novels to film, like Bride and Prejudice (2004) was adapted by our popular culture.
D.W. Griffith's films, especially "Birth of A Nation" and "Intolerance" were monumental acheivements for the time. The themes, photography, actors, and overall stories made and continue to make huge contributions to the art of film making. "Birth of a Nation" is told and photographed in a wide variety of styles; from huge scenes with thousands of extras to the vignettes that show the individual perspectives of people in situations that reflect the human condition. His scenes were poignant, controversial, (as he shot sequences of the Ku Klux Klan (portrayals) and the intentional poor treatment of black people at the time. This caused a lot of outcry from the black communities and organizations, such as the NAACP at the time. However, when looked at objectively, it is clear that Griffith was showing what was actually happening in the nation at the time. "Birth of a Nation" is a monumental epic that has withstood the test of time. Critics and modern film makers are facsinated with these early films by Griffith. "Intolerance" was almost seen as a retort to those who criticized his use of scenes involving racism in "Birth of a Nation." "Intolerance" clearly "spoke" about what Griffith's views on man's inhumanity to man were. It was and is diffcult for people to be subjective when evaluation forms of art , such as these films. The bottom line is that Griffith's films are considered masterpieces of the cinema, are extremely poignant, and continue to spark discussion and debate among film-makers, film-historians and scholars.