This is where border adjustments come into play. We can, for example, implement a carbon tax in the US and impose a tariff on goods from other countries depending on their own environmental policies. This serves as a way to put pressure on all countries to reduce greenhouse gas emissions together.
In fact, the EU is in the process of doing this right now, and China is definitely reacting to it (not happy, but it seems like the Chinese government is looking toward expanding their existing policies to cover more industries in an attempt to avoid the EU border adjustment).
Another way to look at it is that given how much the USA has already contributed to the accumulation of greenhouse gases, China would need to continue at their current levels for another 30 or so years before they catch up with us -- and that's with about 4x the population.
I understand that that argument may not be persuasive to some, though, because a lot of the manufacturing and technological development that took place in the USA over that time benefited many countries. And a lot of those emissions took place prior to the wide knowledge of how serious climate change is.
So I'd really say that we should aim for net zero emissions because it's the right thing to do. Everyone has to do it, and it's not going to happen if we all stand around waiting for someone else to go first. There is a pretty massive amount of emissions cutting we could do without much effort at all, and if the rest is spread out over a number of years, the cost will be very small, and will have a lot of benefits to people's health. (Climate change is not the only negative externality of burning fossil fuels by a long shot.)
The place to start is a carbon tax. I highly recommend that everyone who cares about climate change call congress (https://citizensclimatelobby.org/call-your-representative-ab...) and ask them to support a carbon tax.