Mills and Clement combined for six one-hit innings and minor leaguer Brien Dopirak's two-run single in the ninth gave the Blue Jays a 6-5 victory Wednesday.
Philadelphia's Jimmy Rollins had a two-run double in a four-run eighth that put the United States ahead 5-2.
"I'm glad I got those extra ABs, " Rollins said. "I needed some rhythm. It took me a couple of at-bats but I finally got it."
"Obviously, the thing that hurt me was the walk," the left-hander said. "When I don't throw strikes, it gets back to haunt you, no matter who you're playing, whether its United States or not. "
The right-handed Clement, who hasn't pitched in the majors since rotator cuff surgery in September 2006 while with Boston, would have had three perfect innings had it not been for first baseman Kevin Millar's two-out error in the sixth.
"Both of them did a good job for us against a tough team," Toronto manager Cito Gaston said. "(Mills) is a tough kid out there. He has the right makeup for it. He doesn't rattle out there at all."
Mills was a combined 13-5 in Class-A and Double-A last season,
"This is my first big league camp, and I've been in pro ball for a year-and-a-half now, so it definitely probably the toughest lineup I've faced," he said. "You try and tune all that stuff out. Honestly, I don't even look at those guys up there. You can't look at them in the face or anything, just focus on the (catcher's) glove and control what you can control, which is just throwing strikes. I try to simplify it as much as I can."
"(Rollins) said he wanted to play, and that was good," United States manager Davey Johnson said. "A lot of the guys have said that third and fourth at-bat is really crucial in getting their timing and feeling comfortable."
Dopirak started Toronto's comeback in the bottom of the eighth, then the Blue Jays pounced on Mets right-hander J.J. Putz in the ninth.