In the 2019 patch/upgrade there are quite a few scenarios that pit either the US or the USMC against the Japanese, they are hard to fight against but not impossible. Use tactics that Andy suggested above. I'll have a small (2-3 companies for the USMC vs. 3-6 from the Japanese) on Guadalcanal around Alligator Creek in a 4-5 Mini-CG out in 3-4 weeks if you'd like to test that out.
Here is the USMC (I recommend playing as USMC against the Japanese until you're ready for a challenge, then take the USA, Russia or GB, ANAZC) as player one for 2019 (via the default sql query supplied, I can provide more info later):
Code:
ScenarioID Title
499 Wilkes Island, Wake, 12/41
500 Tanambogo Islet, 8/44
50 Into The Valley 10/42
512 Lambeti Plantation 6/43
625 Raider Ridge 6/43
49 Stark and Bitter Hours 11/43
492 Tarawa Atoll, 11/43
513 Tarawa's Crimson Tides 11/43
73 Return to Guam 7/44
501 Guam, Marianas, 7/44
401 Peleliu #1, D-Day 9/44
402 Peleliu #2, D-Day 9/44
403 Peleliu #3, D-Day 9/44
404 Peleliu #4, D+1, 9/44
405 Peleliu #5, D+1 9/44
502 The 1,000 Yard Stare 10/44
503 Split Down the Middle 10/44
63 Iwo Jima: First Ashore 2/45
64 Iwo Jima: Sever The Head 2/45
65 Iwo Jima: Take Suribachi 2/45
66 Iwo Jima: The Meat Grinder 2/45
457 Iwo Jima D-Day 2/1945
495 A Common Virtue, 2/45
518 Charlie Dog Ridge, 2/45
67 Iwo Jima: Last Gasp 3/45
And these are all the ones where the USMC is defending (or player two):
ScenarioID Title
Code:
498 Wake Island, 12/41
691 The Rock 5/42
39 Bloody Ridge 10/42
516 Matanikau, Guadalcanal, 10/42
386 Bougainville 11/43
400 Tarawa, 11/43
490 Solomon Blues, 11/43
Personally I think that 625 and 691 would be good USMC vs. Japan scenarios but I am biased since I created them
Attached is all the scenarios (in the 2019 patch up to 3/27/2019) where Japan is player two.