so 10 on 30-35 is more about 30%. And those wouldn't even have bad connection, but 170-200, what all eastern euros have in us, and those south americans have 170-200 in us too, so no difference for them anyway.
The actual ping cfg of servers is more about that :
in us, us have 35 ( min ) to 90 ( max ), euros 130 ( min ) to 220 ( max ). South americans have about 170 - 250.
In euro, euros have 15-50 ( 70 for laggy people ), us 90 ( min ) - 130, and it seems south americans 170 - 200.
So basically euro servers have better pings.