I recall reading somewhere that an allied victory in WWI was inevitable, with or without US assistance, it just would have taken longer. The RN blockade was starving Germany and while the French and British were both bleeding their empires could still be cannibalised to keep going, where Germany had lost most of hers and definitely any access to them.
I have also read that US industry benefited massively from transferred technology, processes and procedures from the UK and Europe. For example the faulty RN shells we hear and read about so often were actually predominantly sourced from the US prior to their factories getting up to speed on the latest quality standards. There is a school of thought that in two consecutive world wars the UK and Europe bankrolled the expansion and modernisations of, not only their own industries but also, US industry. I am not suggesting in any way that the US was behind or backwards, rather that circumstances handed them, lock stock and barrel, the full sum of British knowledge and expertise on top their own. Had the US stayed out of it they would have received none of the benefits of foreign orders boosting their own expansion and modernisation efforts, none of the technology transfers, tactical insights, access to detailed battle and damage reports, let alone intelligence obtained from the Central Powers.
The flipside is France and Britain would have bled deeper and for longer and would have had to make greater use of their empires, the British in particular having to invest in their larger, richer dominions to obtain what the US was not supplying. Thus Canada primarily and to a lesser degree Australia and NZ would have seen their industries expanded and modernised to make up for short falls in the UK. Many of the tactics used to end the war had been developed earlier than they could be effectively used due to lack of material, in particular artillery, this short fall was eventually made good by the US, had they stayed strictly neutral the short fall would have had to have been made up by the dominions meaning that all they treasure and credit the US earned during WWI would have ended up within the British Commonwealth instead.
The war would have lasted longer, losses would have been greater, but the allies would still have won and the wealth and IP transfer from Europe to the US would not have occurred. Also the US would not have earned the international prestige of being on the winning side and likely would not have had the diplomatic and financial weight to drive the Washington naval Treaty meaning the UK likely would have called it instead with a somewhat different outcome in terms of ship size and numbers.