Like what?
What will benefit the American for it? It's not like EU are not going to change their supplier, whatever Russia do or not do, EU are not going to stick with Russia like before, the door is already opened up. You don't need to blow up the pipeline to reopen it again.
On the other hand, would Russia even have money to maintain the pipeline? Now that it earn 0 for them. Better that got destroyed and crawl some money back then have it just sat there and lose money everyday.
Like :
Geopolitical :
1. Ensuring the Russians will no longer have any carrot / leverage in any future negotiations with EU / Germany.. Lessening the possibility that Germany will negotiate or pressure the US / Ukraine to negotiate with Russia in the coming winter or beyond.
2. Ensuring that the EU states can no longer change their mind regarding not using Russian gas, even if under pressure from their own populace and industry.
3. Ensuring that any future gas export (after the war settles and peace returns) from Russia will have to pass to through Ukraine / Baltic states, paying billions of $ for transit fees.
4. Showing the world that the US "walks the talk" when declaring the US can and will stop the NS2 from delivering.
5. Personally humiliating Putin, as NS2 was his dear pet project and deterring the EU from even considering similar projects (with any country) without US approval in the future.
Economic :
1. US will replace Russia as the main energy exporter to EU, ensuring additional billions of profit for US gas, oil, shale industries.. at least for the short to medium term.
2. Energy intensive EU industries will run out of steam (literally), forcing them to wind down, close or relocate offshore where energy are plentiful and prices are low... potentially receiving the relocated EU industries into the US...
3. Decrease global competitiveness of EU industries and products due to high energy prices... Would Airbus planes cost much more now...? Perhaps that can help Boeing that's not performing too well lately..?
With the coming winter and energy hardships / rationing, the European resolve may begin to falter in the face of cheap Russian gas dangling in front of their eyes.. especially if this winter turns out to be harsher than usual and their population angrier... By crippling NS1 & NS2 that carrot is no longer available... thus the US gains all the benefits from this sabotage while the cost are practically nothing...