As David's answer indicates, the split between Enter and Return reflects a longtime difference in labeling between IBM/Microsoft nomenclature (Enter) and Apple nomenclature (Return). Although the MacBook keyboard you photographed includes both return and (in smaller letters) enter as labels on the key in question, my iMac keyboard from 2014 includes only the label return.
I worked for many years at a PC magazine, where we consistently identified the key as Enter (as IBM-compatible computer keyboards did), and for several years at a Mac magazine, where we consistently identified the key as Return (as most Apple products did, albeit in lowercase). The fact that your MacBook even acknowledges that enter is a legitimate alternative label for return suggests that Apple may be facing the reality that Enter is the more widely recognized label for the key—because PCs are still far more common than Macs.
I think that a complete switch from Return to Enter on Apple keyboards is still unlikely, even in the post–Steve Jobs era, because it would raise the prospect of Apple's having to deal with the knottier issue of reconciling the key labels in the lower left corner of the keyboard with their PC equivalents and remapping various keystroke combinations—steps that many longtime Apple users (I imagine) would vigorously oppose. Few things reinforce Apple users' prejudice against PCs (and PC users' prejudice against Macs) like having to get used to so many keys having the wrong labels, so many controls being in the wrong place, and so many keystroke combinations being needlessly different.
In any case, to answer your question, Enter is the label more familiar in U.S. English (and indeed throughout the English speaking world). But there is nothing wrong with saying, on first occurrence of an instruction, something along the lines of "...and then press Enter (or on a Mac, Return)," and thereafter simply "...and then press Enter."