There will never be a "US divided corpse," we are one people and one nation. We might lose Alaska and Hawai'i simply to geo-political concerns, but the lower 48 will be forever united. There are many ethnic groups within our nation, but we are all Americans.
We are divided by irreconcilable ideological differences on many issues. Equal rights for Homosexuals, Abortion, Immigration Reform, Health care, issues on education, and so forth and so on. These schisms will tear our country apart. Civil war will not come because of ethnicity or by a cluttering of states, but due to our ideological differences that swarms in every population.