The victory gave Spearmon, who missed out on a medal at the Beijing Olympics when he was disqualified for a lane violation, a chance for redemption in London.
He said he planned to make amends even though that means he will have to outrun Jamaicans Yohan Blake and Usain Bolt.
"It (the disqualification) is definitely something that has been on my mind since 2008," said the 27-year-old Spearmon, who missed most of last season with a hamstring injury.
"It is hard enough to make one Olympic team. To go and make the finals, step on the line when you thought you had a medal, take about 300 meters of the victory lap and then have to live with that.
"If I had not made the team this year, that would have been on my mind for the rest of my life."
Spearmon, close friends with Bolt, said he was surprised Blake and Bolt were not faster in the Jamaican Olympic trials final on Sunday.
Blake ran 19.80 seconds with world record holder and Olympic champion Bolt second in 19.83, times which the outspoken Spearman said he, trials runner-up Maurice Mitchell (20.14) and Isiah Young (20.16) could match.
Top U.S. sprinters Tyson Gay, Justin Gatlin and Walter Dix did not contest the event, leaving many to believe Spearmon is the only real medal hope for the Americans against the might of the Jamaican team.
Not so, said Spearmon.
"Everyone expects Jamaica to be 1-2 but we could go out there and get first, second and third," he said. "The sky is the limit."
Off the track, the highly controversial third place dead heat in the women's 100m finally appears headed for resolution.
Allyson Felix and Jeneba Tarmoh will compete in a runoff on Monday to determine the last U.S. sprint spot, officials said.
It will take place nine days after the original race.
Meanwhile, Michael Tinsley ran down twice Olympic champion Angelo Taylor to win the men's 400 hurdles in 48.33 seconds, the slowest winning time at the trials in 40 years.
Taylor, in making his fourth U.S. team, clocked 48.57.
Olympic silver medallist Kerron Clement took third in 48.89 over a stumbling Bershawn Jackson.
Jackson, the Beijing Games bronze medallist, missed the US team by 0.05 seconds.
"It's a heartbreaker for me because I have a family to support," said Jackson.
World champion Lashinda Demus came close to the year's fastest women's hurdles time with a dominating run of 53.98 seconds.
"Missing the team in '08 was heartbreaking. It was a burden on me and I definitely have unfinished business," said Demus.
Double world long jump champion Brittney Reese had a close call, her last-round leap of 7.15 meters ruled a foul before she protested.
"I looked down at the mark (on the long jump board) and didn't see anything so I am happy that I won the protest," said Reese. "We are ready to sweep."
Collegian Chelsea Hayes had the lead at 7.10 until Reese's big jump. Janay DeLoach also made the team at 7.08.
Leonel Manzano took the men's 1,500m in 3:35.75 to narrowly beat world bronze medallist Matt Centrowitz, who clocked 3:35.84 with Andrew Wheating third in 3:36.68.
Morgan Uceny controlled the women's race in 4:04.59. Shannon Rowbury (4:05.11) took second with world champion Jenny Simpson (4:05.17) rounding out the US team.