I went to a music camp that had "classes" in the actual universities for young people(ages 13-18) . So you can imagine my knowledge of music history in certain periods of music isn't as advance as yours. I just know basic outlines and the well known composers. So anyways I remember the "teacher" said there's an argument when the romantic period started. They say 1810 or 1819 or when beethoven's ninth symphony came out(1822-1824). However I like this argument because it is safe to say this was the early influence or the beginning of the period that would eventually spread across the western world in music. Since it's known that things were slower back then , therefore it took longer for everyone to know of these "new" things,ideas, or beliefs.
I also remember learning how politics played a role in music back then. I found 19th and 20th century music changing those roles as well. Since a lot of the music back then were commissioned by the royal courts of europe, whomever was the favorite composer would get the most recognition. Then in the 19th century you had the downfalls of a lot of monarchies. Therefor I can definitely see even small remnants of favoritism in music by leaders playing a role in music back then more then you see today. I don't really recall anyone caring who obama likes but everyone sure hell cares about what magazines , mtv, tv in general , web sites , advertisements ( remember being bombarded with kreyshawn "gucci gucci" ads on youtube) or any media for that matter recommends now.