Diplomatic priorities for the US can be quite complicated, and sometimes inscrutable. One constant high priority, however, is selling weapons made by America’s major arms-makers to other countries. Though private companies, they increasingly find the US diplomatic corps working as their sales team.
This represents official determination to see the US remain the world’s largest exporter of weapons. This is a foregone conclusion with or without diplomats hectoring every other country to buy American, and attending weapons shows to push US products.
Since April, there have been reports that the Trump Administration was advancing from the arms dealing being an unspoken side mission to an overt policy goal for all overseas diplomats. In practice, a lot of this means scaring nations away from buying cheaper Russian systems on the grounds that the US will be mad at them.
Yet Russia does continue to have some successful segments of the arms market, particularly the air defense systems. While military officials believe Russian sales are just going to happen sometimes, the Trump Administration has had fits when nations like Turkey, despite all the diplomatic pressure, choose to buy Russian.