The difference being, of course, that a DirecTV receiver and its dish is a physical thing, easily identifiable and somewhat bulky.
A smart TV looks a lot like a TV. Given there over 60,000 bars in the USA, it is naive to believe that a situation dis-similar to what went on in the wild-west days of the BUD will not exist.
It is easily enforceable. All that matters is whether NFLST games are shown on the TVs in the bar. If they haven't paid (one of) the company(s) legally entitled to distribute it under a commercial public viewing license, they are showing it illegally and will be sued.
Smart TVs, receivers, etc. are totally irrelevant to this.