Yes, when you look at stats on Project-GC (your own or someone else's), you will see them using the measurement system you have set in your preferences. The measurement system used when exporting profile stats for use on your geocaching.com profile page is (as Target says) defined by the Export language setting in the settings on the Profile Stats page itself. Note that language works in the same way with one setting for what you see yourself and another for what gets exported.
Don't slam the US for hanging on to imperial. Neither Myanmar nor Liberia have changed over either. At least not officially. ;)