I would think the NFL would be attractive to any investor. The issue here is that the billionaire international class that is interested in sports-franchises-as-toys are almost exclusively Russian and Arab. They're not as interested in our sports accordingly. Though I would expect a Russian billionaire to own an NHL team at some point. Of course, that is if the entire league they own in Russia gets boring. But my assumption is that this is just a matter of time and opportunity. If Abramovich could buy the Yankees, don't you think he would? Expecially if it's simply all about prestige. The significance of the Yankees isn't lost on an international audience - even if baseball is.
In order to make a major professional franchise work, there have to be large concessions from the state, county, or municipal government involved. That is, there are usually some tax writeoffs granted, help with obtaining land, a portion of stadium construction and operating costs paid, and so on. At the very least, there is assistance given in the form of access roads and parking. For a local owner, or even one from out of town, these things are usually, albeit grudgingly, granted to some degree. I'm not sure very many government entities would be quite as willing to support foreign ownership. But then, I suppose that if they'll do it for automobile factories, they'll do it for a football team.
Maybe if Abramovich throws a high-end escort service into the mix, he can get the guv'nor to push through a Yankees sale?