Nothing is ever as simple as simple minded people would like to have it. First, the "yank engine" blurb. Here's your most proven all American Yank engine having a bad bad day:
AA 767 High Pressure Turbine Failure That incident totaled the 767 it was hanging from during a routine engine run test on the ground. Left main tank emptied completely onto the ramp due to several large puncture holes into the lower wing surface skin. Try having THAT happen to you half way across the pacific... with a YANK engine, a GE CF6-80.
Second, the airlines' equipment purchasing decisions are largely influenced by their marketing department since a while ago. All of that number crunching means nothing and will be worth jack sh!t when your competitor flies a more attractive product in direct competition and you have to lower your seat price to be able to sell seats on your 'less attractive to customers' aircraft. Do you think the general public know anything at all about Boeing vs. Airbus ? All they will ever know is how comfortable the interior of it is, period. Larger cabin, more inflight conveniences, the allure of flying on a 'super-jumbo jet' or whatever fancy name they decide to call it, etc... If marketing cannot sell the product, everything else means nothing. And no airline in their right mind would ignore the wishes of it's sales team over number crunchers when the sales team says "we can sell this product for this much and that one for this much less". That's how it works in the airline industry. Good or bad. Nothing new.