Gregg Berhalter has held tightly to his preferred system, often manifesting as a 4-2-3-1. Rarely does he deviate from this and even he does, it often is a tweak rather than a whole cloth change. When not using his preferred formation, he's turned to a 3-2-3-2 and more recently a 3-4-3. The numbers may change, but the effect remains very similar.
I've long considered the similarities to British composer Edward Elgar's Enigma Variations. It may seem far fetched on the surface to compare soccer tactics to late-Victorian classical music, but the comparison is in how they approached their work.