To be clear the letter doesn’t say that the US should support proprietary ISAs, in fact it doesn’t even say US persons cannot work with someone in China on RISC

To be clear the letter doesn’t say that the US should support proprietary ISAs, in fact it doesn’t even say US persons cannot work with someone in China on RISC-V (or other open architectures). They are suggesting that for a US person to work with a person or institution in China, they must first seek a license from the Dept. of Commerce. This would be like if in 2005 the US said that if you wanted to accept patches from China, for Linux, you needed their approval to do so. This doesn’t make it good policy though. Our allies will be stuck in the crossfire and basically have to choose between Chinese RISC-V or US RISC-V. US export controls are very far reaching and apply to re-transfers, which requires a sustained administrative infrastructure to avoid violating. As a result European satellites and space hardware for example completely avoid using US parts to derisk compliance. What export licenses will ultimately do is isolate the US.