Except the top colleges like MIT, stanford, etc, most foreigners get into US colleges because it is an easier path to get a work visa in US, that's it. Also, the 70k h1-B are currently working in US, so they pay US taxes. If they are not allowed, most of the work will be outsourced (and a lot of that has already been), so it will be a further loss to US.

Also, India uses human resource as a balance in trade. They allow US companies to sell stuff in India in luie of them highering indians abroad (which send a part of the salary back home to their family) or in India. If US applies an America first policy in everything then India has no incentive to allow these companies into India. Software companies are not creating super critical things which can't be replicated, specially by indians who are already working for Google, Facebook, etc who will lose their jobs.

EDIT : Currently there are no tariffs on Tech companies. What are people even arguing ?