When you hijack a usa dozer get a rax as well as power. Spam md's with your quads and it's pretty much gg.
Second ad also wasn't very smart; against a usa with decent micro your not going to kill his vees with quads so once he has a decent army of vees they become useless. Your much better getting a palace and going for buggies.
When you've got a usa on the back foot use it to take map control. Take the oils (which you did but were pretty slow) and the middle. Means if you can't finish usa off you've got something to fall back on.
Very nice start but a couple of poor choices gave him the chance he needed.
