Where in the Bible does God get mad at some people for mixing and marrying outside their own tribes? Does God think that marrying another race (tribe?) is wrong?
Christians are not under the Old Covenant, but rather under the new one. In the New Testament, there is no prohibition against mixed marriages of the sort you have in mind. The prohibitions in the Old Testament were meant to try and protect a tiny minority religion from the polytheism and immorality that existed all around Israel.
—Ben Witherington III