A Ukrainian operative based in Poland suspected of the attack disappeared just before Polish services got to visit his place. Wouldent be surprised if they waited for him to pack; Poland was doing everything it could from Nordstreams being built.

to deepen their dependency

Temp situation, and would be short sighted as a strategy. UE has big gas resources of it's own (Norway, Ireland, "neighboring UK"). A few countries like Karat or Armenia (if I recall correctly) are looking to export gas to EU as well. Which was, according to a Russian general, the reason for their involvement in Syria. And still - EU is very actively working on shifting out all fossil fuels. Diplomatic risks for US outwaight possible benefits.

severely damaged German industry

Russia cut deliveries before the pipeline were blown up. Also the EU did not stop buying Russian gas, it capped the price. The thoughput of the currently operational pipes is enought as well, but doesent allow to blackmail Ukraine or Poland. And finally Ukraine is shutting down them, to further demolish Russian profits.

US naval vessels were operating in the immediate area of the bombing, and were conducting underwater “training” exercises in the week leading up to the bombing.

Source?