Many native americans look asian, it depends on the tribe. In fact, all pure blooded native americans originate from asia because thousands of years ago, they migrated across the bering land bridge between Russia and Alaska (This was long ago before the continents separated), hence how humans (evolved out of sub-saharan africa) could be in north america despite not having the technology to cross oceans.
Cos the animator didn't have much practice drawing Abos probably. They have an ENTIRE TEAM of animators drawing each frame painstakingly , anyone who mess up a frame will show. So they picked a style everyone has drawn before.. and that's asian.. That's my theory.