| It's impossible to say with such certainty what the reaction would be. What if the country that developed it was a Western-aligned country like Japan, Israel or France? What if the country was a country like Russia or Cuba, and has had this tech since before the fall of the Berlin wall and the US intelligence community wanted to keep it secret? What if the country was a country that is under Western sanctions for other reasons but those reasons were a pretext? For example, if the developer was Iran or North Korea how would you tell the difference without access to classified information? What if the country was able to blackmail the US into not imposing sanctions? How would you distinguish between that an US foreign policy towards a country like Pakistan or Saudi Arabia? What if the country was a historically neutral mid-power where there is significant downside in sanctioning them (for example Switzerland)? What if some elements of the US intelligence community support working with the foreign power and others don't? There are just too many possibilities to judge the veracity of a theory like this by looking at US foreign policy? |
In the above situations, it'd be imperative for the US to acquire the tech through war, economic pressure or espionage, or if that wasn't possible try to prevent them manufacturing more. If it was a friendly country they'd have to share the tech.
This tech is basically like developing 5th gen fighters in the Stone age. There's simply no way the world's largest superpower wouldn't acquire the tech by any means necessary, since it threatens its very existence