If I am not mistaken strategic bombers can climb up to

the altitude where fighters can't reach.

I might be still stuck in WW2 air strike strategies/mind. To my knowledge strategic bombers are used only to undermind opponent's morale and confidence by destroying/ruining strategic targets such as factories and military structures. If a war between two huge countries really occurs they will be the pioneers (escorted by fighters). Ambush only achieves local victories against them not the whole air fleet get affected.