Would a USB hub help? - Probably not but possibly.
First step, ensure both ends of the XLR are fully seated on their connections. Ensure that the +48v is engaged and the LED light shows that it is on. Check that the microphone does not have a "pad" button that is engaged.
While talking into the mic adjust the "Mic Gain" until the LED just above it is a good solid greed while talking and when you get loud it should turn it yellow - turn it down if it's going red.
Next, plug in headphones to the Shure X2U adjust the monitor volume dial and listen to see if you hear a nice loud sound level when talking into the mic.
Once you have that you know the unit itself is getting the right volume level and skip the next 2 paragraphs.
If it's not getting loud enough at this point there are a few possibilities.
In the order of least to most likely 1) The Shure device is bad 2) The mic is bad 3) the XLR is bad 4) the USB power to the Shure X2U is insufficient to give enough phantom power (+48v) to the mic.
If you suspect number 4 is your issue you can make sure you've got powered USB ports. That's fairly standard now and should provide enough power. The Shure X2U requires 500ma from the computer's USB power. (check the PC's manual or support documents from Dell's site) The mic needs 7ma of +48v and the Shure X2U says it can put out up to 10ma of that phantom power. Trying a powered USB hub that you know sends out good powered ports might be worth a try. They usually indicate the amount of power output for the powered USB hub's ports on the specs page. Trying all of the different ports on the PC is also a good idea. Even though all the USB ports plug in the same they might not all actually be the same on the PC.
If you had good sound through the headphones then it's time to check settings on the PC. Right Click the speaker icon on the taskbar > Open Sound Settings > on the right hand column select "Sound Control Panel" > Select the recording tab at the top of that window > Click the Shure X2U device > Properties > Select the Levels tab > This is hopefully already at 50 if lower start by adjusting it to 50 and test. Keep turning it up and this should get you to the right level.
It should also be noted you might want to make the Shure X2U your "default" recording device and make sure your software is selecting that device or the windows default in it's options. It would be terrible to find out it had selected something else like a gaming headset sitting far away on the desk this whole time.
All of these steps should be fairly similar to most XLR to USB devices.
