In other words: your perception of your quality of life would have to have unreasonable roots (such as a large, disproportionately wasteful car and needing to consume large amounts of relatively low quality chicken and pork) in order for you to actually experience a decline, rather than just change.
Otherwise, what motive do most Americans have to reduce consumption? Even people who believe climate change is real and are worried about it likely barely move the needle. That's before we even consider people who don't believe or don't care.
Now, I think we can reasonably meaningfully reduce the amount of pollution we produce per "unit of consumption" such that consumption levels could remain relatively unchanged, but still allow us to save the world. Whether or not we can get there, with powerful short-term-thinking, status-quo-loving lobbying groups hindering progress every step of the way, is another matter.
There are lots of things, primarily in the domain of corporate regulation and incentives, that we can do to reduce per-capita pollution. Plugging externalizations, in turn, has a virtuous effect on demand (since businesses will push some of the costs onto consumers, and consumers will respond by maximizing purchase value over longer timeframes).