Upwork, it's one name that springs in my mind. And as any marketplace, it has its slackers and hard workers.
If they are good, they have already moved to the US or some other higher income country. There’s probably a “good quality foreign contractor” living down the road from you.
A significant amount of people don't like to move really far away if they don't have to.
As someone that decided to stay (even after getting visa sponsorship offers), not necessarily (although Uruguay is probably a "higher income country" these days).
Although the good contractors are SWAMPED for work, I definitely have to up my rate.