Europe is "taking a lead" in phasing out the use of diesels?  You must be joking.  Over 50 percent of passenger vehicles sold in the EU are diesels.  They've become so prevalent that the European cities you mention have no choice but to ban them because the smog they produce, due to less stringent European emissions standards, has become intolerable.  Their prevalence is due to their greater efficiency and lower CO2 emissions - basically, the Europeans have chosen to address climate change at the expense of air quality.