Not neccesarilly.
Humans evolved in Africa, but that does not mean that they all stayed there. There were people that left and went over the land bridge into America at one point. How could they have been bred into the European mix? Are you saying that I am related to every single Native American if all of my ancestors (I can trace them back to the 1500s, so I know that they are not related to any Indians) have not married or had kids with Native Americans? I am not saying that the great majority of the world is not related, but there are at least a few people that are not related to any extent (the population of the Earth would have to have at least a few of these people, due to the sheer amount).
Also, "inbred" involves at least a mildly close relation. You can only really say that someone is "inbred" if their parents have "at least a couple cousins over" relationship. Beyond that, the genes that are passed on are barely, if at all, similar (unless by chance). The mere fact that all humans may have come from the same continent, and have all married eachother at one point or another does not mean that they are all inbred.