There are many factors that influence site selection for a U.S. Open championship in future years. I will try to clear up a few misconceptions, if possible.
The primary drivers, all of which must be present:
First, the venue needs to have a large amount of physical open space outside the ropes for the huge needs of television, corporate hospitality, merchandise tent, media facilities, security and other infrastructure that is required to stage a major championship. It is far, far greater than the weekly tour stops. This tends to favor sites that have other courses adjacent to the championship course. Once in a while they can bring the championship to a physically "tight" space like Merion but they give up millions of dollars in hospitality revenue and ticket sales in doing so.
Second, the golf course itself needs to be a supreme test of golf. This is our national championship. It's not the Humana Classic. These players are incredibly talented. It takes a special golf course to test all aspects of the games of the best players in the world and worthy of hosting our national championship. The USGA has been pretty good about finding venues that are great venues and have not held a US Open since Hogan hit his one-iron, and are great tests--Bethpage, Pinehurst, Torrey Pines, Chambers Bay, Erin Hills are examples.
Third, the U.S. Open has an impact on the community. The USGA needs cooperation of the governing bodies of the communities for things like parking, police, fire, transportation, etc. Sometimes the governing officials are not very cooperative (imagine that) and can kill a potential bid. This has been an issue with Torrey Pines getting future consideration, at least to this point.
Fourth, there most certainly is politics involved. But the USGA has to be invited by a potential site, and some clubs don't want it. Hosting an Open can put a golf course out of commission for an entire golf season, particularly if significant renovations are required. Other sites have a very well coordinated, years-long lobbying effort to host the US Open. Call it politics if you want, but the USGA wants to take the championship to places that want very much to host it.
So you add all that up, and the list gets pretty short. Weather can be a factor to be sure, but the USGA doesn't rule out a site because it's hot in the summer. They like to move the championship around geographically, so if we had a site that had everything in place mentioned above, there is a possibility it would be considered. But unfortunately, we don't, and on top of that, it's hot here in June, so the reasons cited above plus the weather are why places like Texas, Arizona and Florida are unlikely to host a U.S. Open any time soon.