Multiple outlets stopped working after wall-mounting TV
In wall electrical cables very often do transit from one wall stud cavity to another by passing through a hole bored through the stud. If you happened to drill a pilot hole for your lag bolts right into one of these cable pass through holes there are at least four possible things that could happen:

Nothing. The drill bit and bolt miss the electrical cable completely
Short. The drill cuts into the electrical cable in such way as to cause a hot to neutral short. This probably leads to a few sparks and the circuit breaker tripping in the panel.
Cut Hot. In this case the drill bit could have damaged the electrical cable to cut open the hot wire. Any downstream electrical outlets on this same circuit very well may end up being unpowered.
Cut Neutral. Similar to the Cut Hot case this can effect down stream devices/outlets on this circuit. This could lead to a very dangerous situation at down stream devices/outlets with an &quot;open neutral&quot; condition. This is particularly a problem if the circuit is a Multi Wire Branch circuit with both phases of the source power feed are fed down the same cable.

There are also other issues that could come up related to any GND circuit conductors may become shorted to either the hot or neutral wires. This can also be dangerous and would most likely to trip upstream GFCIs or GFCI breaker at the power distribution panel.
If you are not equipped to handle the problem isolation or have limited experience with this subject it may be advisable to bring in someone experienced in the field to help diagnose the problems. The potential dangerous situations with this are very real and should be addressed in a serious concern.