She headed home a Kristine Lilly free kick to open the scoring in the 30th minute, and the U.S. added goals by Lilly, Lindsey Tarpley and Heather O'Reilly to win going away. The U.S. outshot Finland, which had lost, 1-0, to the U.S. in March at the Algarve Cup, by a 38-2 margin.
In the next U.S. Algarve Cup match, against Sweden, Boxx made her comeback official.
"Shannon is looking like herself again, which is fantastic," said U.S. coach Greg Ryan. "She's one of the best in the world at set-play goals. She looked like a forward tonight taking players on. I think she likes it here."
Said Boxx, "My first cap was here. My first goal was here. This place will always have a special place for me, and I will always remember my first goal with the national team."
Lilly's assist is the 100th of her career; she and Mia Hamm, who along with Julie Foudy were inducted into the U.S. Soccer Hall of Fame Sunday, are the only U.S. players to hit the century mark in goals and assists.
"It's nice," said Lilly. "It helped us score a goal, that is always good. It's always good when you can help your team win and hit some milestones along the way."
The team is scheduled to depart for China Monday. It opens the 2007 FIFA Women's World Cup against North Korea Sept. 11 and also meets Sweden and Nigeria in the first round.
"I thought that we had a lot of energy in attack tonight," said Ryan, who used all six of his allotted subs and replaced Abby Wambach, who jammed her toe in the 27th minute, with attacking midfielder Carli Lloyd.
"We said let's just roll up our sleeves and go after them in attack. It's important to carry that kind of spirit into the World Cup. We are going to go after teams and if they can hang with us OK; if not, we'll just keep swinging until we can knock them out."
Aug. 25 in Carson, Calif.
USA 4 Finland 0
Goals: Boxx (Lilly) 30, Lilly (Chalupny) 36, Tarpley (Rampone) 68. O'Reilly (Lloyd) 76.
USA - Solo, Rampone, Whitehill (Jobson, 84), Markgraf (Ellertson, 79), Lopez, Boxx (Wagner, 79), Chalupny (Osborne, 76), O'Reilly, Lilly (Kai, 74), Tarpley, Wambach (Lloyd, 27).
Coach: Greg Ryan
Finland - Korpela, Vaelma (Pyhajarvi, 69), Salmén, Julin, Niemi (8- Saari, 28), Lehtinen, Valkonen, Koivisto (Vartiainen, 84), Puranen, Hokkanen, Sjolund (Sallstrom, 60), Talonen (Hokkanen, 90).
Coach: Michael Kald
Referee: Kari Seitz