What background music is being played in this MR PRESIDENT | RUINED video?
The music playing in the background of that video is Fig Leaf Rag by Scott Joplin.
It is a form of Ragtime music from the late 19th century. Scott Joplin was dubbed the "King of Ragtime" and was known for composing piano music during this time. Typically it is played on an upright piano like those found in saloons and speakeasies during that era.