China's economic threat has magnified several fold because the US has spent the past 2 decades mired in conflicts that have been stoked by its allies in Saudi Arabia. Meanwhile, China has had a free hand in developing trade relations with its neighbouring states and African countries, further weakening the US' position there.

Whatever billions the US has earned selling weapons to KSA are a drop in the bucket compared to what it's spent in Iraq, Afghanistan, Yemen, Libya and Pakistan. These are all countries where KSA has funded extremist political movements that continue to destabilize the region.