M777 is foremost more expensive (since made of titanium), while less critically reviewed (actually…

Re. what USA plan: actually, it's irelevant. Important is (or should be) what Ukrainians plan and, thus, need.

M777 is foremost more expensive (since made of titanium), while less critically reviewed (actually, it nearly fell through during US Army's and USMC's testing in Afghanistan, especially when intensivelly deployed). However, 'it must be kept in production to save jobs' (read: to save profit). Thus, let's donate some (paid by taxpayers) to Ukraine, while buying many more of them.

Re. what USA plan: actually, it's irelevant. Important is (or should be) what Ukrainians plan and, thus, need.

Since when is 'weakening enemy air defences' the aim of a war?

Aim of a war is winning a war. Not 'weakening enemy's air defences'.

Otherwise, one is fighting endless wars.