Just because the US 8th AF brass in 1943 wanted to believe in the firepower of an unescorted box formation didn't mean a capable escort fighter wasn't available.
Had Hitler not ordered the ME-262 redesign as a bomber and it was available in 1943, I don't see where much would have changed.
The P-38 Lightning was available.
When compared against the ME-262, the P-38 had a slower horizontal speed, much higher climb speed and comparable dive speed.
The Lightning had significantly better low speed performance and had a significantly higher service ceiling than the 262.
In all probability, 262 pilots in 1943 would have been under orders to avoid contact with fighters. The 262's prime target in 1943 would have been bombers and all escorting Lightning had to do was interrupt the 262s pass on the formation.
If the 262s were attacking alone. If in concert with 109s and FWs, P38s would have been at a disadvantage. Of course 51s would have been along as well. Thw 262s real threat aside from closing speed were its 30mm cannons converging at, I think 800m.Solid burst would rip a 17 apart.