Conrad Fondrk (St. Paul, Minn.) started the scoring 4:42 into the opening stanza with a power-play goal. Trethewey got his stick on a rebound and made a quick pass to Fondrk on the doorstep, who tipped it past El Paso goaltender Joey Lovullo to take a 1-0 lead. Cullen Potter (Minneapolis, Minn.) earned an assist on the goal as well.
Will Belle (Minnetonka, Minn.) doubled the U.S. lead just past the halfway mark of the period, snapping the puck from the left circle off a no-look feed from Cole McKinney (Lake Forest, Ill.), who carried it into the zone after connecting with Donny Bracco (Freeport, N.Y.) at center ice.
Back on the powerplay, Andrew O'Neill (Fargo, N.D.) picked up a loose puck and found Fondrk behind the net, who dished it to Trethewey at the top of the right circle. He sent home a one-timer to give Team USA a 3-0 lead.
The Rhinos got on the board with 2:09 left in the period as Alex Bernauer knocked a rebound home.
Jack Murtagh (East Greenbush, N.Y.) was the next to score for the U.S., stealing the puck from El Paso on the penalty kill, skating down the left wing and firing from the high slot with a nifty toe-drag move with 3:41 to play in the middle frame.
Trethewey picked up his second power-play goal of the night with just over a minute left in the period after connecting with Asher Barnett (Wilmette, Ill.) across the zone, skating into the high slot and beating Lovullo with a wrister. Potter also earned an assist on the goal.
Tory Lund scored a second for El Paso 4:23 into the final frame and Jakub Jerman brought the Rhinos within two just shy of the period's halfway point, but El Paso was unable to complete the comeback as Team USA skated away with a 5-3 win.
Harrison Boettiger (Wheat Ridge, Colo.) saw the first two periods in the U.S. net and had 34 saves on 35 shots, while Patrick Quinlan (Kennett Square, Pa.) closed out the final 20, stopping 12 of the 14 he faced.
The Under-17 team is back in action tomorrow night for their second game of the NAHL Showcase as they take on the New Mexico Ice Wolves at 7:00 p.m. ET.