They've done so (at least partially) by moving the bulk of their industrial production into the 'developing' world.

The US has dropped per-capita emissions even when you include the emissions from offshored production: https://ourworldindata.org/consumption-based-co2

To levels that are still much higher than India.

This didn't happen purely because Western countries became more aware of their impact on the environment. As countries develop, their population growth rate slows. Their technology improves and they can spend energy more efficiently.

In the US's case, there was a large gain from switching from coal to natural gas for power generation. Not because it was better environmentally, but because it was cheaper. It's disingenuous for the US to go "Look at all we've done" when half the country is in firm denial that there's even a problem.

Interesting how recognizing success in lowering carbon emissions gets downvoted. I'd like to know why.