The US has yield signs. The yield sign was in fact invented in the US. The first one in the world was installed in Tulsa Oklahoma in the 50s.
It's trivial to make a roundabout have yield signs. Some roads here are like that, where every 4-way intersection of stop signs is now a yield + roundabout. You can theoretically get all the way through without stopping.
But you can't have yields at a 4-way stop. Connecting 2 perpendicular roads at low speed is an incredibly common problem - the US chooses to do it in a stupid way.