That's a non sequitur, totally unrelated to my comment. But I'll play along....
First of all, civil unions aren't equivalent to marriage. Two, even where they were available weren't recognized in all states. Three, why do you care what it's called if it is equivalent...or close enough?
Call it "marriage" and everyone in the U.S. knows what it means, what rights it entitles the couple, and their obligations. The courts, government agencies, IRS, creditors, home buyers and sellers, banks, hospitals, and more are all dealing with the couple from a position of certainty if it's a "marriage." If it's a civil union, who the hell knows what that means, especially if they were "unioned" in CA and the couple is in Alabama or Tennessee that didn't recognize civil unions.
Point is, why not just call it "marriage" and afford gay couples the SAME rights, and obligations? If you want less than that for some inexplicable reason, you'll have to explain why.