155mm ammo isnt very relevant to a defense of Taiwan. The US isnt going to deploy 20 divisions there. This is a job for the Navy and Air Force.
And extended firing of artillery isnt in the cards even for the Taiwanese. They need to repel the Chinese on the beaches, and that will be over quickly, win or lose.
The artillery, GMLRS, anti-tank weapons, etc are doing exactly what they were designed and produced to do. Kill Russians. Invasion of Taiwan is a completely different war. Meanwhile, not a single Main Battle Tank, Infantry Fighting Vehicle, SRBM, Fighter Jet, advanced UAV or Air Defense system (beyond MANPADS) has been delivered to Ukraine. These are weapons that could significantly change the war.
It seems to me that 155 mm arty w/ long range guided munitions would be pretty rough on an invasion fleet.