The US President needs to punish NATO allies for his or her stance within the Iran struggle, and his Foreign Minister Marco Rubio is bringing the closure of US bases in Europe into play. That would have drastic penalties.
https://www.spiegel.de/politik/deutschland/usa-donald-trump-und-marco-rubio-warum-standorte-wie-ramstein-entscheidend-sind-a-7e041b80-320b-45e4-a1b8-e0fb153d79d0#ref=rss