The chart above is from a recent Gallup Poll -- done between November 9th and 13th of a random national sample of 1,019 adults, with a 4 point margin of error.
It shows that 77% (more than three-quarters) of Americans believe the United States is currently a divided nation, while only 21% see it as united. Both of those numbers are records for the Gallup Poll on this question -- with 77% being a record high for divided, and 21% being a record low for united.
I think that 77% is exactly right. The question, of course, is whether Donald Trump can unite the country. I seriously doubt that he can, but a surprisingly large number believe that is possible (45%). More say he can't though (49%).