I think it's the other way around. The international version has "IATA" in the name, as in "IATA Cabin Trolley", and has dimensions of 21.7" H x 15.7" L x 7.7" D.

You refer to 'domestic' as US. Rimowa is not US, however, and does not make any US-specific models.

It looks like what you have is the Cabin Multi-Wheel, and that is larger than the IATA version. I'm pretty sure you can use this larger version on most US flights, as US carriers don't usually enforce their own rules. Some luggage manufacturers have international and US versions of carry-ons. The US versions are usually larger.

You would have probably fine with the larger version.