My coach, Steve Smith, was a world champion for the US in sambo. Steve Nelson was on the same national team as him--and I believe some other names. He posted a photo of the "old days" on Facebook and there were a number of guys I recognized, I think.
Its funny--in a single session, he taught me stuff about leglocks that I will never forget. And also taught me things about grappling in general in a way where I didn't always realize at the time how much I was getting.
At the gym I was training at, there were a lot of young guys that, like me, spent a lot of time lifting weights and loved grappling and basically thought that we were big shots. Coach Steve, with his gray hair, glasses and easy manner, would anihilate all of us on the mat. I think there are about 3 people I can think of who were as functionally strong as him.
BTW--I think there have been a few sambo world champs from the US, though of course, mostly I just know about Coach Steve.