I know the answer for the 2nd world war. The political parties and formations were all pro allies except three notable formations which are:

German American Bund
Was a nazi organization supported by germans in USA, evolved simultaniously with the NSDAP, but never got enough support to have any notable power. When the war broke out, the organization became unfavored in many ways, they were inspected of missing taxes, and later they refused to be drafted so the members got fined for USD 10000 and 5 years in jail, later, by the mid-late war the leaders got jailed or revoked citizenships etc, so the whole organization stopped working.

Silver Legion of America
Was a fascist party in USA, ran in elections of 1936, but never got really over than 10000 members, right after Pearl Harbour, the local police occupied the HQ of Silver Legion and the membership of the party left as the war went on.

And one more notable and popular organization is America First Committee with spokesman of Charles Lindbergh, who flew over the Atlantic ocean. They wouldn't enter into the war on Axis side, but strongly argued against entering in any side, namely the Allies side. I mention them, because if their points get approval like opposing the Lend Lease Agreement, being neutral, etc... it could seriously affect the outcome of 2nd world war.

So for the side of the second world war: there were no doubt if USA is a pro-allies power, these organizations were in small minorities when Pearl Harbor occured, most of people supported the allies' cause.

I know the answer for the Second World War. The political parties and organizations were all pro Allies except three notable groups:

German American Bund
This was a Nazi organization supported by Germans in the USA. It evolved simultaneously with the NSDAP, but never got enough support to have any notable power. When the war broke out, the organization became unfavored in many ways: there was a tax investigation, and later they refused to be drafted so the members got fined for $10000 and 5 years in jail. By the mid-late war the leaders were in jail or had their citizenship revoked, so the whole organization stopped working.

Silver Legion of America
This was a fascist party in USA which ran in the elections of 1936, but never really got more than 10000 members. Right after Pearl Harbor, the local police occupied the HQ of the Silver Legion and the membership of the party left as the war went on.

And one more notable and popular organization is the America First Committee, which boasted famous aviator Charles Lindbergh as a spokesman. They wouldn't enter into the war on the Axis side, but they strongly argued against entering on any side, even the Allies'. I mention them, because if their points had gotten approval — such as opposing the Lend Lease Agreement, or being neutral — it could have seriously affected the outcome of the Second World War.

So for the Second World War: there was no doubt that the USA was a pro-Allies power, as these organizations were a small minority when Pearl Harbor occurred, and most of the people supported the Allies' cause.

I know the answer for the 2nd world war. The political parties and formations were all pro allies except three notable formations which are:

German American Bund
Was a nazi organization supported by germans in USA, evolved simultaniously with the NSDAP, but never got enough support to have any notable power. When the war broke out, the organization became unfavored in many ways, they were inspected of missing taxes, and later they refused to be drafted so the members got fined for USD 10000 and 5 years in jail, later, by the mid-late war the leaders got jailed or revoked citizenships etc, so the whole organization stopped working.

Silver Legion of America
Was a fascist party in USA, ran in elections of 1936, but never got really over than 10000 members, right after Pearl Harbour, the local police occupied the HQ of Silver Legion and the membership of the party left as the war went on.

And one more notable and popular organization is America First Committee with spokesman of Charles Lindbergh, who flew over the Atlantic ocean. They wouldn't enter into the war on Axis side, but strongly argued against entering in any side, namely the Allies side. I mention them, because if their points get approval like opposing the Lend Lease Agreement, being neutral, etc... it could seriously affect the outcome of 2nd world war.

I know the answer for the 2nd world war. The political parties and formations were all pro allies except three notable formations which are:

German American Bund
Was a nazi organization supported by germans in USA, evolved simultaniously with the NSDAP, but never got enough support to have any notable power. When the war broke out, the organization became unfavored in many ways, they were inspected of missing taxes, and later they refused to be drafted so the members got fined for USD 10000 and 5 years in jail, later, by the mid-late war the leaders got jailed or revoked citizenships etc, so the whole organization stopped working.

Silver Legion of America
Was a fascist party in USA, ran in elections of 1936, but never got really over than 10000 members, right after Pearl Harbour, the local police occupied the HQ of Silver Legion and the membership of the party left as the war went on.

And one more notable and popular organization is America First Committee with spokesman of Charles Lindbergh, who flew over the Atlantic ocean. They wouldn't enter into the war on Axis side, but strongly argued against entering in any side, namely the Allies side. I mention them, because if their points get approval like opposing the Lend Lease Agreement, being neutral, etc... it could seriously affect the outcome of 2nd world war.

So for the side of the second world war: there were no doubt if USA is a pro-allies power, these organizations were in small minorities when Pearl Harbor occured, most of people supported the allies' cause.