Didn't check the specs but I'm pretty sure the Meteor, Shooting Star, P-82 and probably a few other super props would've been able to deal with the MiG 9.
DH Venom (or Vampire? I confuzzle 'em). The Avro Lincoln. Comet tanks. It's not like USSR is only fighting one nation now. They're only fighting the two most powerful economies in the world.
A few potential U.S. jet types:
Douglas XB-42, Ryan FR, McDonnell FD
And yes, the DeHavilland Vampire was about to appear on the scene in the closing days of WWII.
The following new aircraft types entering service in 1945 come to mind.
Britain
Supermarine Spitfire XXI - first two squadrons converted in April / May 1945
Gloster Meteor - still in low rate production of Mk.III. 616 squadron received these in Jan 1945 followed by just 4 other squadrons in 1945 (April, June, July, Oct)
De Havilland Vampire - first production aircraft only flew on 20 April 1945 and early aircraft were not pressurised. Few (a dozen?) available by Aug 1945. First squadron formed March 1946 with two more in Oct 1946.
Lincoln - Only cleared for service use in Aug 1945 with 3 delivered to each of two squadrons for trials in Aug/Sept. It was April 1946 before it was accepted for full squadron service.
Hawker Tempest II - first 2 squadrons converted to type in Aug 1945
Blackburn Firebrand TF.IV - first squadron formed 1 Sept 1945
USA
Vought F4U-4 Corsair - began to reach squadrons about April 1945
Grumman F7F-1 - was beginning to arrive in the Pacific in Aug 1945 as land based photo recce and night fighter
Grumman F8F-1 - Bearcat - VF-19, the first squadron went to sea in Sept 1945
Ryan FR Fireball - first squadron, VF-66 received them in March 1945 and was still working up when the war ended. Only unit equipped with the type.
Lockheed P-38M - the nightfighter version
Lockheed P-80 Shooting Star - First unit, 412th FG on verge of deployment to Pacific in Aug 1945. Another 30 aircraft shipped to Philippines in summer 1945 lacked wing tip fuel tanks so not issued until 1946. Type was grounded by end of 1945 due to accident rate.
McDonnell FD-1 / FH-1 Phantom 1 - first production contract awarded 7 March 1945 for 100 later cut back to 60. Production was slow taking to 1948 to complete. 1947 before the first squadron was formed to operate these.
P-82 - only flew in prototype Packard Merlin engined form in April 1945. Only 20 P-82B (of 500 on order) flew before the end of the war.
Jets on carriers.
Due to engine characteristics there was grave doubts in 1945 as to whether they could successfully operate from a carrier deck. The RN made the first jet carrier landings and take-offs on 3 Dec 1945 with a modified Vampire on the light carrier Ocean. The USN deck landed a jet for the first time in July 1946 with the FH-1 Phantom 1, on one of its largest carriers, the Midway class Franklin D Roosevelt.
Tanks
Comet - 29th Armd Brigade, 11th Armd Div converted to these in spring 1945 and used them in the final campaign. 22nd Armd Brig, 7th Armd Div began conversion in summer 1945.
Centurion - 6 Mk.1 arrived in Germany for trials just as the war in Europe was ending. Full production began in Nov 1945
M-26 - Some 2,200 were produced in 1945 with only a few reaching Europe before VE-Day. Plans were in hand for deployment in the Pacific in time for Operation Olympic
IS.3 - Production of this Soviet tank began in summer 1945, and made its first public appearance in Sept.