The US is devastated demographically. The war OTL was worse than than WW1 was for the British. TTL, I imagine that the casualties will be more in line with France, in the end. So you have that playing in as well. The US will be exhausted... And may take a line that is reminiscent of France after the war - no quarter given.
This demographic crunch will really hurt the US, as the OTL Civil War caused the US to pull inwards. But, here, the US has been shown that it cannot successfully and safely do so, so it must retain a military force that can ward off foreign aggression and it must eliminate avenues for aggression as well.
In the event of US victory in the war, I imagine that the southern states were forcefully reincorporated against the British. After all, the rebellion now has transitioned to open treason with the support of foreign adversaries. At best, the reconquered states might be offered leniency if they return to the union and fight against the foreigners. The ones that do not return (the deep south) will end up being treated far more harshly than the others.
On top of that, at least the prairie provinces will be taken, along with the Pacific Northwest, as the US cannot risk a resumption of hostilities in that theater. Lower Ontario may be another region that the US desires, and border provinces may be annexed. Simultaneously, Quebec may be liberated as an allied republic in the north. Ideally, the US would prefer ownership of the Lakes in total, but everything else could go to this larger Quebec. As for the Maritimes/Newfoundland, these are most easily held by Britain, and simultaneously they would be one avenue the US could prepare for. Aside for some border adjustment, I don't see these being taken as peace would be sued for and the US would be tired of war once the country is liberated and Canada falls to the west.
This US would, at a minimum, be forced to update and maintain its fortifications and maintain a navy. It owuldn't have much more than a few ocean-going cruisers, but I definitely see it expanding its monitor fleet ot be second to none, making the mainland effectively impregnable to most oceangoing vessels for decades. This would be interesting come the time of the Virginius affair, if something like that occurs TTL, as the US would be well suited and well-inclined to assist the Cubans this time around.
Reconcilliation is not impossible, though it becomes much harder. If anything, I imagine the US being anti-European intervention in general. So they'd be supportive of Germany, but only in the sense that they'd oppose British expansion.
At the same time, the US would be very enthusiastic in maintaining its sphere once it does venture out. It may be more enthusiastic about pressing its Guano Island claims, with Hawai'i, etc, as it cannot allow the British a Pacific equivalent to Bermuda to raid the West Coast again. As for the other claims, once the US gets its feet back under itself, combined with a much stronger navy, it could be more aggressive. That's where any Germany alignment is called into question as the two are competing in the Pacific and Germany wanted to expand in Latin America OTL. That has to be addressed before anything else happens.