The use of uncle sam to represent the us is often use in political cartoons this is an example of which technique

The use of Uncle Sam to represent the US is often used in political cartoons is an example of symbolism.

Explanation:

Symbolism is a technique that uses symbols to give symbolic meanings to ideas.  

Uncle Sam is a popular symbol for the US; It was purposefully designed to interpreting and framing political discourse and national identity.  Uncle Sam is a very influential and iconic symbol of America, it is used to represent the American nation in foreign press; it was also present in War recruiting posters. In all, is a familiar symbol of patriotism and government of the US.