The US is growing slowly, but doing so at a consistent pace. It will keep growing 2% indefinitely.

I'm not claiming this. Nothing can.

China is growing faster now, but the rate is slowing year over year. They will grow 5% this year, 4% next year,... The implication is that they'll eventually settle domewhere below the US for (preferred boogeyman reason)

Pretty much this, without the boogeyman reason. I'm not claiming a reason. I don't even think it'll be below US levels necessarily, but it won't keep growing as fast as it was. The trend is pretty steady, for the US and China, though things of course change and it's probably logarithmic I'd guess, not linear. It'll steady out somewhere. (Edit: Well, it'll steady out per capita probably, which is part of why GDP is so useless. It's not measured per capita.)

https://www.statista.com/statistics/263616/gross-domestic-product-gdp-growth-rate-in-china/

There's no need to make things up. Either China (and any other country) can stand on its own or it can't. People shouldn't be mislead. Now, I don't think GDP is that useful, but I didn't start the thread about GDP.