A USB Wi-Fi adapter will only work as well as the signal it receives from the router. With the metal cases that surround most desktops, and the myriad of wires that supply power and data between the devices of a typical desktop, it is quite common for the available USB port that will accommodate the adapter to not be in an optimal location for maximizing signal strength. Add in the additional interference from nearby Wi-Fi networks and, in situations where the router is not in the same room as the computer, some signal strength optimization is often required.
Thankfully, there is a simple fix for this. A short (24” often works well) USB extension cable can allow a rear USB port to be utilized for the Wi-Fi adapter, while allowing the adapter to be positioned far enough away from the case, and in the direction of the router to gain signal strength. Such cables are available inexpensively, and can be indispensable to optimize the location of the antenna in relation to the router.