It makes very little sense for the CSA to be a match for the USA after their WWI. Before WWI sure. Canada is there. The Royal Navy is around. A CSA that is slightly more than half as strong as the US but with allies that sort of surround the US could be a threat.
But even if the US allowed the CSA to regain their military (unlikely) Canada is gone. Yes keeping that under arms wouldn't be cheap but hey Quebec is sort of friends. And I find it very doubtful that the UK would get involved in a sea battle with the USN from Newfoundland (I think they stayed independent since how the fuck would the USN conquer that island?). So yes a lot of 19 year old with rifles might be in Canada but the barrel and planes would be relatively light.
Also why is Japan fighting the US? The US is not in the Philippines. Their Pacific presence other than Hawaii is pretty light. Heck switch sides and attack the French and UK during WWI and steal some of their territory. Germany and this US isn't really going to care much about what Japan is doing in China and Germany would LOVE a medium power who is opposed to Russia as allies (call it a lucky guess here). If Germany and Japan had any "hey we want this island' disagreements I think Berlin would be willing to give in fairly easily. Again what is there other than Hawaii to take from the US and German alliance? I understand that Japan and the UK sort of had an alliance in OTL but friends with Russia?
And lastly why did the US take Hawaii anyway? To put themselves into conflict with Japan? This US was not in the "banana republic" sugar plantation business like real US was. Any attempt to strong arm Latin America countries (yes I know Hawaii is not in Latin America) would be stopped by the CSA and more importantly the UK. It just seems to me that this USN would be smaller and with a lot less battleships. Submarines, destroyers, and cruisers sure they would be useful to harass shipping to Canada and the CSA. But battleships? And more to the point would this USN have the logistical skill to force the UK out of The Sandwich Islands? TL-191 USN is not much of a blue water force.
Taking Newfoundland should be fairly easy for the USN, the vast majority of the RN heavies are going to be staying in the North Sea to watch the HSF. If the RN built as many battleships as OTL it would be all of them, assuming they built more, they might free up some, but to the RN the North Sea is 1st priority, unless the RN is more than 50% larger than OTL in battleships, a single USN battle squadron and escorts should suffice to escort a Newfoundland invasion
The USN would want a lot of battleships, and given that the Union States in 1914 have both a higher population and a higher GDP/Capita than Germany, the US could afford a larger than High Seas Fleet sized force and an equivalent to the German Army at the same time. And having two thirds of that that as a fleet in being in the Atlantic would strain the RN's ability to punch troops convoys through to Canada, as they have to escort very heavily. Destroyers don't harass blue water shipping, as they lack range and seaworthiness, and no one prior to WWI conceived of the sub (also short ranged at this time) as anything but a defensive tool
As for taking Hawaii, flank protection for the sea-route to Chile and their Saltpeter, which until 1914 (and the Haber process) is absolutely a do or die in any war over 6 months, escorting against CSA's light units is easy, escorting against RN heavies out of Hawaii would wear the PacFleet out fast. Logistics are difficult admittedly