That's not nothing but also not that high relative to some other things. Addressing this is not going to do much to solve the overall problem that the US is emitting a lot of CO2. AI usage is probably going to grow over time. But it will have to grow a lot to get to displace e.g. transport, industrial heating, or agriculture as dominant sources of CO2 emissions.
Short term the tendency of AI data center providers to solve their energy needs with gas powered generation (mainly) is not great of course. It's opportunistic, there's extra underused gas generation capacity currently that's more or less readily available.
But long term there are some obvious cost savings there as well. Gas isn't cheap; even in the US. And gas turbines are actually scarce. Increased demand is hard to meet with just gas for this reason. AI data centers aren't picking the cheapest energy source but the easiest accessible energy source. Some companies are even looking at nuclear. And not because it's cheap. Likewise, some companies are apparently considering doing some AI compute in space (solar powered).
Long term, solar, wind, and batteries are likely to be the cheapest way to source energy in this sector as well as is already the case in other sectors. Energy is one of the largest cost components for providing AI compute and competition is likely to be fierce. There's no way that companies dependent on expensive forms of energy will be able to compete long term. The short term game is about grabbing market share. Surviving long term will require aggressive cost savings on energy generation.