The 23-year-old striker ran out at the Hong Kong Stadium on Wednesday a day after learning that his first coach, Josef Schulz, had lost his battle with cancer at the age of 61.
Altidore told the Sunderland Echo: "For me, it was always going to be a difficult game. It was probably the hardest game of my life because on Tuesday, I had some bad news.
"The guy who got me into football lost his fight with cancer. Everything I've known has come from him, so it was a really difficult game.
"But I was happy that I could play and show the guys that I'm committed. That was the biggest thing for me, to show I care and that I'm committed.
"I'm a private guy, I haven't really talked about it. I didn't care if anyone knew about it.
"But these guys have been working so hard that I owed it to them to go out on the pitch and give something to them."