Diplomatic expulsions are a standard if extreme way of showing outrage. But tactically speaking, they have mixed results.
https://www.foreignaffairs.com/articles/russia-fsu/2018-04-03/when-diplomats-and-spies-must-go
http://theweek.com/articles/764699/what-does-trump-want-from-putin
https://republic.ru/posts/90298
http://www.kasparov.ru/material.php?id=5AC3C68A2D3EA
https://www.gazeta.ru/politics/2018/04/03_a_11704340.shtml
https://www.kommersant.ru/doc/3591642