Williams’ performance on the station’s annual Capitol Fourth program Sunday evening is intended to celebrate the recognition of Juneteenth’s establishment as a federal holiday.
"It’s in celebration of the wonderful opportunity that we now have to celebrate Juneteenth. So we are reflective of the times," the actress and singer, who was the first Black woman to win the Miss America Pageant, told the Associated Press.
"We are reflective of the times and I’m happy to be part of a tremendous show that the producers are aware and willing to make the changes that have happened within the past year and a half."
Her rendition of "Lift Every Voice and Sing" will not replace the U.S. national anthem, which will be sung by Grammy-award winner Renée Fleming, but it has still bitterly divided people on social media.
"Vanessa honey, a BLACK national anthem is something a Black African Country would have, not a country like America that exists for everyone," Spicer tweeted.
Author Tim Young echoed Spicer’s concerns, tweeting: "Nothing will unite us more as a nation than separate but equal national anthems…"
"This isn’t unity… it’s division," Young reiterated in a follow-up tweet.
Jenna Ellis, the former Weld County, Colorado, deputy district attorney and Trump lawyer, invoked the words of the Pledge of Allegiance to show her frustration.
"We are ONE Nation, under God, indivisible, with liberty and justice for ALL," Ellis tweeted.
"We’re witnessing the unraveling of E pluribus unum in real time," former CIA officer Brian Dean Wright fumed, referencing the traditional motto of the United States, which is Latin for "Out of many, one."
"The consequences will be dire," Dean Wright warned.
Other social media critics also railed against the decision to perform two anthems.
"I didn’t get the memo, we have a new anthem? And what was wrong with our original one?" one Twitter user responded to the announcement.
"What? I thought we were ALL Americans?! Now divided by color? What happened to one nation, under God, indivisible? Talk about dividing us…" another said.
Originally called "Lift Every Voice and Sing," the song was written by NAACP leader James Weldon Johnson in 1900 and was popular among Civil Rights activists in the 1950s and 1960s.
A Capitol Fourth will air on PBS from 8 to 9:30 p.m. EST.
The 41st airing of the celebration program will also feature Jimmy Buffett, Gladys Knight and Train.