Nevertheless the balance favors Germany even if it means they give up the Uboat campaign;
I take it you mean the unrestricted campaign.
Something often overlooked is that losses to u-boats were climbing fast even before USW was adopted. By Jan 1917 (the last month before USW) they had already tripled from the level of a year before.
If the Jan 1917 level were maintained through 1917, total sinkings that year would be around 4.4 million. True, this is a big drop from the 6.3 million of OTL, but it's still more than 1914, 1915 and 1916 put together, and the reduction will be easily offset by the drop in imports from the US due to the financial problems already discussed, and to the poor US harvests of 1916 and 1917.
Then there is the sticky issue of the Wilson administration finally being willing to confront the Entente over the blockade issue in 1917; after cutting of loans to the Entente, US businesses wanted trade with the continent again and Germany had amassed a large gold stockpile during the war. Without the declaration of war glossing over this problem, by mid-to-late 1917 the US will be pressing the Entente on the issue, which they will have to back down on or face the prospect of USN escorted convoys of merchantmen seeking to dock in German ports.
Agreed, though I doubt if such convoys would attempt to go directly to Germany. Both sides had sown the North Sea and Balltic so thick with minefields as to make this an extremely dangerous undertaking. But from the Allied pov, convoys to Holland or Norway would be just as bad.
I'm also doubtful whether such convoys would try to force their way through the blockade - that would be risking an exchange of shots between British and US warships, which I shouldn't think any US Administration would want. However, if they were turned back, the US might well have said "If we cannot sail freely in these waters, we will not sail there at all", and ended all such sailings, laying down that if Britain wanted US goods, she would henceforth have to send her own ships for them. This could be important, since it would make USW a far safer option for the Germans. If no American ships are entering British waters, then clearly none can be sunk there, so USW, though it may still attract American disapproval, will not lead to a head-on collision.
It is often overlooked that (Allied-US and especially Anglo-US) relations would not have stood still in 1917. Until Germany "changed the subject" by adopting USW and sinking US ships, these were bad and getting worse due to arguments over blacklists etc. Some kind of economic reprisals are a distinct possibility if American neutrality is maintained.
Food exports, as I've already mentioned, are liable to dry up even without government action, simply because American food is all being consumed at home. The other big export (even bigger than munitions) is cotton. Wilson probably won't embargo that, as it would hurt his Southern supporters, but Hughes, if elected, would not have that particular consideration.