Lots of countries can make excellent weapons, so what?
Sweden made great steel in the 1940s, they sold it equally to the Allies and the Nazis.
Did you know the NYPD has more cops than Sweden has soldiers?
How does their joining NATO benefit America?
My preference is that NATO evolve into something else, maybe split into as many as three alliances. As it is its obsolete, however that’s a different discussion. Since NATO is not going away, this adds two states that at least pay their own way on defense unlike Germany. Of course, we’ll probably volunteer to relieve them of much of that burden.
No, they don't. Swedes have a bit more than 50k compared to 35k NYC cops. As to what good they could do, that's somewhere around 30% of the force with which Russia invaded Ukraine, so it is significant when added to the forces of other allies.
Benefits the U.S. by adding to the strength with which Europe can provide for its own defense.