In Donald's case, he happened to be living in Japan in the early 2010s, and responded to an ad looking for reps to work in China, then realized exactly what they meant by that. "I was at a press conference with city officials once for a ball bearings company, and our contact had given me a short speech about trade. When I sat back down, our contact said to me, 'Good job,' but then he turned to the Chinese official next to him and said, 'We found a good foreigner' ... I asked him in the van on the way back, 'Why did you need me here today?' He said, 'Because with you, it makes them look like they're rich. That they have connections. That money can come in with Americans.'"
It also just makes a company look better in general -- it implies they have international reach, maybe higher standards of quality. It's kind of like if your friend told you his crazy business idea landed him a meeting with "investors from Silicon Valley." The phrase implies that real money is at play.
They'd even have Donald play up the "brash, loud American" bit, encouraging him to raise his voice and use a lot of hand gestures, bringing flair to a meeting that would be considered rude if it came from locals. One company was recovering from a fire, and the plan was for the Chinese leadership to show they were appropriately chastened in front of the staff. Then Donald's role was to do what only a supposedly wealthy, white investor could: "In that meeting, my Chinese 'co-workers' held the same ashamed sort of face, and me and a Canadian were like Tim Robbins pumping up this company. If foreign investors are still supportive after a small disaster, it shows the company has staying power, and that's what we were there for."