It's more fun to come up with combinations from other teams, IMO.
Canada
Andrew Wiggins
Jamal Murray
Tristian Thompson
Kelly Olynyk? Cory Joseph? Nik Stauskas?
Dominic Republic
Karl Anthony Towns
Al Horford
Fransisco Garcia
Louis Montero? Charlie Villanueva?
Haiti
Nerlens Noel
Skal Labissierre
Samuel Dalembert?
An unknown guard?
Brazil
Leandro Barbosa
Maybyner Nene
Tiago Splitter
Fab Melo? Lucas Noguiera? Anderson Varajao?
Germany
Dirk Nowitzki
Dennis Schroder
Paul Zipser
Carlos Boozer? Chris Kaman?
Spain
Marc Gasol
Pau Gasol
Ricky Rubio
Nikola Mirotic? Serge Ibaka?
France
Tony Parker
Rudy Gobert
Joakim Noah
Nicolas Batum
Australia
Kyrie Irving
Matthew Delladova
Patty Mills
Dante Exum
Croatia
Bojan Bagnonovic
Dario Saric
Ivaka Zubac
Justin Hamilton
Obviously, Canada would have to be the second ranked team after whoever America decides to send. As for #3? France? Spain? Looking at who is currently in the NBA from different countries to make up a 4 man roster makes things interesting.
For fun, USA
LeBron James
Stephon Curry
Russell Westbrook
Anthony Davis
Draymond Green?
Kevin Durant?
Kwani Leonard?
What a hard time it would be selecting 4 players for such a tournament. I'd want the most athletic big available, the best one on one scorer, and the best 3pt shooter. That's how I ended up with my four. I figure Westbrook would make for a great jack of all trades if I needed to sub out someone. You could put James inside for AD without much penalty at all or swap Westbrook for either James or Curry without upsetting the differences in size or ability much at all. Westbrook can go one on one or be a sharpshooter.