That would be ideal, and maybe possible: "Unlike the connector and inlet, which depend on the geographical location, the charging communication is the same around the globe" Combined Charging System - Wikipedia
The newest Model S/X, and the Model 3/Y are capable of CCS signaling (in europe they are, and I'm 100% sure they didn't develop specific boards for them). For the older models, there is a retrofit to allow the car to understand the CCS signaling, very simple to install, right under the rear seats. If CCS ever comes to the US, I'm sure it will be the same.
The US spec 3 and the EU spec 3 have totally different controller boards for charge port communications. Damien Maguire has a video that shows them side by side, search youtube for his "Tesla Model 3 Charge Port Hacking : Intro" video and go to about 9:30 in. It makes sense, the US Tesla charging standard is a very different and simpler (in a good way) protocol, CCS is a complicated mess. The US board is about ~20% smaller and uses a much smaller microcontroller than the UK/EU CCS board.
However, important to note (as you can see in the video above), the charger controller boards are in the same size enclosures and have the same headers, so all the interfaces to them are mechanically identical. So an upgrade to the hardware would not be hard.
Interesting. I wonder if there is something more apart from CCS that differentiates the boards. At any rate, in the worst case everybody would need a simple retrofit.
I did some research (by just comparing the parts catalog of US and a random country in Europe). For Model S/X, it seems that the CCS ECU is required for CCS charging, and the US models lack it, so now I'm almost sure they are not CCS capable. The Model 3/Y situation is different, the charge port controller is not the same, and I would be inclined to think that the CCS protocol was not implemented (because of consistency).