The inexperienced rink – with only Jen Dodds surviving from the 2022 gold-medal winning team – finished sixth in last year’s World Championships and were some way short of their best again against the Americans, with opportunities missed and mistakes made.
A steal in the third end hinted that November’s European silver medallists could get the win they needed, but the US wrested back control to lead at the break.
A double in the sixth edged GB in front again, but the concession of three in the following end gave the Americans a lead that looked insurmountable until Morrison’s late intervention gave them a lifeline.
“Once it came out of Becca’s hand I knew it was close and you see the thrill it gave us,” said skip Sophie Jackson.
“Our performance was up and down but we’ll be back tonight.”
Before then, Britain’s men will return to the ice in a similarly perilous situation.
The world champions must beat the US on Wednesday (13:05) and hope either Italy or Norway lose both their final two if they are to make the medal matches.