I saw on my loop (but did not read) an Islamic attack on Israel claiming they "armed Argentina". Trying to get Brits onside in an anti Israel post.
Truth is, if any country can sell its arms they will to almost any buyer. The US must sell a whole lot of kit to Argentina, as does Israel (and possibly us?). It's just trade.
Take the 1982 conflict. By far our closest and most loyal ally in the conflict was France (certainly not the - at best - ambivalent Americans who were happily supporting an awful despotic Junta). Yet we were being pounded by French made Mirage jets and Exocet missiles.