There are only two tribal casinos in all of Nevada and they're both in the southern part of the state, so they pose no threat whatsoever to the northern Nevada gambling industry. (Northern California Native American casinos, of course, are a different matter altogether.)
Nevada's one major Indian casino is Avi, located on Aha Macav Parkway, 10 miles south of Laughlin. It's owned and operated by the Fort Mojave Tribe of California and Arizona. Avi is a major resort, with a 455-room hotel, 260-space RV park, four restaurants, Colorado River beach and small waterpark, golf course, movie theater, and Kids Quest. The casino, however, occupies a mere 35,000 square feet and has only 800 slot machines and 25 table games. So given its somewhat remote location and minor gambling facility, it's safe to say that any competitive threat it might pose to the Laughlin megaresorts, let alone those in Las Vegas, is marginal at best.
The other tribal casino is Moapa, at exit 75 on Interstate 15 in the eponymous town, run by the eponymous tribe. This slot parlor occupies 2,500 square feet with 100 machines and no table games, so here too, a competitive threat is as good as non-existent.
A score of tribal casinos in southern California, however, impact Nevada casinos to a much greater degree.