I should point out that there are changes that can occur to beer over time, and many of those changes can accelerate with temperature.
One of them, as mentioned, is the fading of hop character. Not a big issue in American macro lagers, because they don't have much anyway.
But other issues could affect taste. Any yeast remaining in suspension or any foreign microbes could cause flavor changes to the beer, and those flavor changes would occur more quickly at high temperature. Oxygen ingress to the beer during the packaging step can lead to oxidation, which gives beer a sort of "sherry" or "cardboard" flavor, and is nasty. Beer does go stale over time [made worse if oxygen is introduced during the brewing, hot-side, processes], and all the staling reactions occur more quickly at higher temperature.
That said, modern American macro breweries should have fully sterile beer, have amazing industrial control processes to avoid oxygen ingress during packaging and avoid hot-side aeration during brewing.
Maybe 30-40 years ago, they didn't, and that's where these myths came from. But a beer from any American macro brewery that experiences room-temperature environment for a week or a month compared to being refrigerated during that time should have NO discernable taste difference.