Replacing an outlet with white black and red wires with a usb outlet with 2 terminals
Here's what's gonna getcha with these types of sockets



That. 

On a normal receptacle, that "Tab" decides whether those two screws are 


merely a convenient splicing block to allow two wires to be spliced together with both sockets in one big happy splice, or 
provide separation of the two sockets so they can be separately controlled.  This is typically done a) because one socket is controlled by a light switch, or b) because it is a multi-wire branch circuit with each socket on a separate leg of power, so two high-power appliances can be plugged in here. 


USB receptacles (least, the ones I am aware of) do not support this separation of sockets. Nor do GFCI or any other specialty kind of receptacle, by the way. 

If the tab is broken off, and you aren't wise to that and just connect the two wires together on the USB socket, then either a) the light switch will stop working, or b) there will be a loud BANG! and a breaker trip. 

In either case, you have to decide which single wire you want both sockets to be powered from, and it either a) decides whether the all the sockets (USB too) are switched by the light switch or not, or b) either hot will suffice. 

However, either way, the other now-orphaned wire must be capped and insulated.