Here is a visual of what the above are talking about
A: As you can see, when you us a US bumper, and install Euro bumperettes, you are left with 4 holes you will need to fill (as I have on mine with plugs from Checker auto parts) Looks cheap, and non cool, but served "my" purpose.
B: As you can see, this bumper had the same issue with peeling paint. Looks to me they put the bumperettes back on when the paint wasn't fully cured.
C: I didn't remove my bumper to get the bumperettes off. I took off the rear apron, and I could fit my big hand into the bumper with my wrench and socket. 3 bolts for each bumperette. I too had the problem of getting them off. I just used some force, and my hands, rocking them up and down, back and forth, and they came right off, along with the paint.
D: The above picture is what my car looks like right now. I went and bought a Euro bumper, so I didn't have to fill in the holes, and to have it right (my personal preference), not that there is anything wrong with using euro bumperettes on a US bumper.