The Wand of the War Mage gives a bonus to spell attack rolls:
While holding this wand, you gain a bonus to spell attack rolls determined by the wand’s rarity. [+1, +2 or +3]
The summoning spells from Tasha's Cauldron of Everything summon an ally that uses the caster's bonus to spell attack rolls when attacking. For example, the Summon Fey spell summon a Fey Spirit with the following shortsword attack:
Shortsword. Melee Weapon Attack: your spell attack modifier to hit, reach 5 ft., one target. Hit: 1d6 + 3 + the spell’s level piercing damage + 1d6 force damage.
Does holding the Wand of the War Mage increase the accuracy of summons such as the Fey Spirit when attacking? If I later drop the wand, would the summoned creature suddenly find itself less accurate?