What can a student do to respond to faculty/administration decisions based on current political events?
As a student, unfortunately there is probably nothing you can do about the situation -- except to remind yourself that one day you might be in a position of power and influence yourself, and able to do things differently.

Things might be different if there were was a particular American professor you wanted to invite to campus for academic reasons. In that case I would express to your chair that you understand his concerns, but talk about what you hoped to gain academically from such a visit.

The immigration ban is strongly opposed by many American academics. If there iss someone particular you would like to invite, you might ask if he/she has done anything to fight the ban (e.g. calling one's senators, participating in protests, donating to the ACLU). In such a situation, your chair might be willing to reconsider. 

That said, I would not recommend pushing the issue hard if at all. You are still a student, and as such you don't have a lot of political clout.