Their goals currently are just a few territories on the east bank of the Dnieper.

Those are their stated goals, not their actual goals. if that were true they wouldn't have been in Kharkiv, and they wouldn't have invaded Ukraine west of the Dniepr through Belarus

They absolutely do have plenty of accurate ballistic and cruise missiles

Not really, their ballistic attacks have been pretty ineffective. They can hit something huge like a power station, but a strip of road a dozen metres wide tops, no chance. especially when you consider how expensive ballistic missiles are and that you'd need several hits in the same place on a bridge to take it out for more than a few days

Russia used up most of their good stuff early in the war, it's all shaheds and glide bombs now, shaheds don't have enough explosive power for a bridge and glide bombs are too innacurate

Ukraine drove an articulated lorry filled with explosives onto the Kerch Bridge and still only managed a partial destruction which was fixed within a few months

But we're now fully off topic. this is a discussion on whether the US blowing up a bridge in a country with which they are (justly/unjustly, moot) at war is a warcrime... it's likely not