Students are not a drain, even if tax payers fund them.
They spend money in the local economy. They help with competition and keeping standards up. They (as others have said) take back useful soft-power propaganda to their home countries.
The ones who leave are a drain compared to students who spend money in the local economy and pay US taxes the rest of their lives. We shouldn't push them away or educate the ones who have no stated intention of staying here. There will still be plenty who leave anyway to propagate propaganda.
They spend money in the local economy. They help with competition and keeping standards up. They (as others have said) take back useful soft-power propaganda to their home countries.