Article indicates that UEFA is part of the discussion and not merely something that was presented to them.
I think UEFA smells an opportunity with FIFA in disarray to strengthen their confederation. It won't be teams like England playing teams like Haiti. The proposal would be for the top league to be compromised of the top European nations, US, Canada, and Mexico. Can almost guarantee that those games would be based on US East Cost and Toronto (maybe West Coast but that nearly doubles the travel time from Europe). Yeah, the medium and smaller European teams are likely to travel to the medium and smaller CONCACAF teams (and vice versa), but I'm sure that UEFA/CONCACAF will adopt the FIFA model and just give them a large enough chunk of the commercials to keep them quiet.
Basically, the financial gain for the big European nations to play meaningful games on a regularly basis in the US is going to be what drives this.
The only question would be if the uproar from European fans (let's face it, US/Canada/Mexico fans would LOVE this) would be loud enough to dissuade UEFA from doing this. But I'm not sure that enough European fans care about the Nations League to put up much of a fuss.