The last thing needed in the US is the TSA expanding their failed model – massive screening of innocent passengers – to other modes of transportation.
https://www.bloomberg.com/news/articles/2016-09-26/congress-wants-the-tsa-to-help-secure-amtrak-and-buses
As documented extensively on this site, massive screening of innocent passengers simply cannot work effectively to prevent terrorist attacks. It is a very sad state of affairs that our congress always reverts to this failed model as a knee jerk reaction to attacks on public transportation.