It follows McKechnie, who is part of the coaching staff at the Braid Hills Golf Centre in Edinburgh, being handed a captain’s pick by DJ Russell.
McKechnie, a three-time winner on the PGA EuroPro Tour, joins automatic qualifier Greig Hutcheon, who will be making his third appearance in the biennial contest, in flying the Saltire on 16-18 September.
PGA Professional Championship winner Matthew Cort booked his place in team along with four other players thanks to their performances at Slaley Hall last week.
Runner-up Daniel Whitby-Smith along with Ashley Mansell, David Higgins and Simon Lilly all qualified through the PGA’s ranking system.
Hutcheon, Simon Thornton and Adam Keogh, meanwhile, had already qualified through the PGA Play-Offs earlier this year.
“I am delighted that Paul McKechnie and James Ruth will be part of our team,” said Russell. “They are both very good players who will fit nicely into what is proving to be a very strong team to take on the Americans in September.
“Both Paul and James performed very well during the PGA Professional Championship last week at Slaley Hall and their form made my two selections a very simple task.
“When you’re picking from PGA Professionals, you’re likely to end up with players who have already played in the PGA Cup, but this year we seem to have quite a few rookies which is brilliant.
“They are all very solid players so we’ll certainly give the Americans something to think about.”
Great Britain & Ireland will be looking to win back the Llandudno Trophy following a narrow defeat at Barton Creek Resort in Austin in 2019.
“I’m very pleased with the final team we’ve got and I’m delighted with the quality we have,” added Russell. “These two picks will strengthen what is already a strong team so we’re now looking forward to the challenge of taking on the Americans at Foxhills Club & Resort.”