Yes, but why would you want to?
War God’s Blessing is an extension of Guided Strike, both are options for Channel Divinity and pull from the same resource pool.
Guided Strike (gained at 2nd level) allows the war cleric to apply the +10 bonus without impacting the action economy.
Starting at 2nd level, you can use your Channel Divinity to strike with supernatural accuracy. When you make an attack roll, you can use your Channel Divinity to gain a +10 bonus to the roll. You make this choice after you see the roll, but before the DM says whether the attack hits or misses.
War God's Blessing (gained at 6th level) allows the war cleric to use a Reaction to apply the same bonus to a creature. The cleric is a creature and always within 30 feet of itself, so it's a valid target.
At 6th level, when a creature within 30 feet of you makes an attack roll, you can use your reaction to grant that creature a +10 bonus to the roll, using your Channel Divinity. You make this choice after you see the roll, but before the DM says whether the attack hits or misses.
A war cleric using War God's Blessing on itself instead of Guided Strike uses up a Channel Divinity and a reaction.
By the time the character has War God's Blessing, it also has two uses of Channel Divinity. I don't see anything that would prevent you from using both abilities to get +20 on the same attack (though there are probably better and/or more efficient uses, like making an additional attack with War Priest and hoping for a better roll); they have the same trigger, but are different abilities so they stack.