https://www.washingtonpost.com/archive/politics/2004/02/27/r...
The U.S. motivation is that it has tried to shut down energy trades between the Soviet Union/Russia and Germany for more than 50 years.
It's worth keeping in mind that the pipeline was also pretty much dormant anyway, the official nord stream data has it that flow collapsed around june, down to exactly 0 (by their books, there was still pressure in the pipe) kWh per day by September.
The pain of seeing a quarter of your industry close for lack of energy might have easily bent the will of Germans and others after this winter. All political announcements about replacing Russian gas before 2027 at the earliest were a pipe dream (pun intended)for anybody with any actual knowledge of the industry.
Even now, a large portion of what was supposedly bought elsewhere was just repackaged and re-originated at the port of loading, but actually Russian gas - hence part of the price hike going to a chain of middlemen.
Blowing it up guarantees Nordstream is forever dead.
The same day a new pipeline was announced as open from Norway to Poland.
Didn't a Polish EU MP tweet "Thank-you USA" when the news broke of the explosions.