The idea that Dolezal's choice to publicly identify as a black woman --- one who occupied positions of power in spaces specifically designated for members of a marginalized group --- is the same as being a trans woman, simply doesn't add up.
What Dolezal did is culturally appropriative, and suggesting otherwise disrupts actual discussions about transgender identity and issues. (It's also worth noting that a white woman's decade-long deception has effectively hijacked the conversation about race, during a week where the nation was focusing on police brutality in McKinney, Texas.)
As Darnell L. Moore of Mic eloquently put it, "In attempting to pass as black, Dolezal falsely represented her identity. Trans people don't lie about their gender identities — they express their gender according to categories that reflect who they are."
Racial divisions may ultimately be a construct, Moore notes, but "skin color is hereditary." And it's skin color that primarily determines racial privilege, and the way others in the world interact with your racial identity.
Transracial identity is a concept that allows white people to indulge in blackness as a commodity, without having to actually engage with every facet of what being black entails -- discrimination, marginalization, oppression, and so on. It plays into racial stereotypes, and perpetuates the false idea that it is possible to "feel" a race. As a white woman, Dolezal retains her privilege; she can take out the box braids and strip off the self-tanner and navigate the world without the stigma tied to actually being black. Her connection to racial oppression is something she has complete control over, a costume she can put on -- and take off -- as she pleases.