I don't think anyone in the US cares that much. And have you seen our foreign policy over the last 20 years? You really don't want us getting involved.
The US didn't randomly, or even out of generic nosiness/imperialism, become a guarantor of the GFA; the Troubles were a focus of intensive and intensely divisive interest in the US.
The underlying forces in the US that made that true haven't gone away.
A more accurate statement: Some career politicians care a little bit. I can guarantee 99% of Americans have no idea what Northern Ireland would be or what border arrangements they do or don’t have with the EU and UK
The US is generally believed to have been the primary source of IRA funding before the GFA. It seems reasonable to assume that Americans care about this issue. You should feel free to ignore the fact that the President-elect and House members representing a majority of the US population have strong feelings about this, since you’ve obviously chosen to ignore this.
Irish americans make up more than 10% of the population. Irish americans are why ireland is free. Irish american money, political power and irish american volunteers were instrumental in winning the war for independence. There are nearly 35 million irish americans. There are less than 5 million irish.
Also, many US Catholics, more generally, have historically, and I suspect that the way the politics of religious identity have evolved recently, that might be even more true than when the Troubles were last active if they became so again.
Yes, I know, my instinct is also to say it's none of their business. But in the case of the GFA, it is.