US Troops Out of Saudi Arabia in 30 Days?!

A new bill in the Senate threatens to remove US troops from Saudi Arabia ion behalf of US oil companies. This begs the question however, if the US really can just threaten to pull out these troops willy nilly, why the hell are they even in Saudi Arabia to begin with?

https://www.reuters.com/article/us-global-oil-usa-senate/bill-would-remove-us-troops-from-saudi-arabia-in-30-days-idUSKCN21R3HG