That part is the 5V regulator.
Remove it, then measure with an ohm meter between +5 and Gnd. Should see a pretty high resistance, like 10s of K-ohms. If not, remove the 328 chip & measure again. If still low, then something else surface mount is damaged - could be the 16U2 USB/Serial chip, the 3.3V regulator, the op-amp, the FET T1 that does the autoswitching.