Earlier quoted context omitted.
The rest of the world should retaliate. (...) EDIT: That was a knee-jerk reaction. Sorry about that.
I think they should only retaliate on US officials (elected and who work for DHS). Ask them to reveal passwords to national secrets when they enter the country, then detain them for hours when they refuse. The general population should be welcomed with open arms - retaliation on them achieves nothing. It's not their fault.
Unfortunately I don't think this will do what you expect - they'll probably happily hand over their password.