The problem is not that foreigners will sue US officials in US courts. The problem is that other countries will pass their own laws allowing their own citizens to sue US officials in their own courts based on their own interpretation of terrorism. Do you really want US political, military and intelligence officials and operators sued in Pakistani, Syrian, Iraqi, Venuezualean courts? And when we lose these cases do you want US assets in these countries siezed by foreign court order? Ironically, the Senate's action may very well subject the United States, in some Islamic countries, to judgements made under sharia law.