US energy use is very high for a number of reasons and energy use will tend to drive CO2 emissions. If you just use electricity (we'll get to that) you can maybe make an order of magnitude difference and maybe if you work very hard, which we need to, two orders of magnitude but that's all you can hope for. That's from 1kg/kWh which is roughly where coal power is, to 100g/kWh and then (very hard) to 10g/kWh with power sources that produce CO2 mainly during construction then amortized over their lifetime.

So if you start out using many times more energy than other countries per capita, you'll struggle to equal them on CO2 emissions even if that's a core policy goal.

The low population density in much of the US drives increased energy usage. I will walk to the nearby grocery store in a few minutes to buy my week's groceries, many Americans will drive, perhaps as much as an hour, to buy their groceries, it's not as though eating is optional. And this low density also forces bad energy source choices (e.g. using wood fires to keep warm seems pretty reasonable when there is no mains electricity out where you live even though of course it's very inefficient)

But to be fair consumerism does not help. Americans have been somewhat resistant to energy efficiency technologies that took off elsewhere, consumption is a sign of wealth and success and so efficiency is in that sense "bad". The entire city of Las Vegas is clearly a terrible idea from an energy efficiency point of view, why would you build a city in a desert?