I’d argue that the drop in conference and other professional visitors could be even steeper. There are still enough people who’ll privately take the risk or aren’t informed or think “I’ll be Ok if I comply with the laws”. Companies or universities however have HR departments and people in charge of travelling and compliance. They would risk a lot more money and possibly secrets if the devices are searched and employees are detained. I think they’ll be even more careful and restrict trips to the US. I could imagine a lot of conferences offering online participation and many opting for that rather than risking it.

And if enough international speakers can’t get in even more conferences will opt for moving the entire conference to a different country.