They would supply both sides with weapons, troops, and financial aid.
The USA and Russia were allies during WWII, but NOT during the American Revolution, no.
To help them win the war. One of the allies that our textbooks never mentions is Russia. King George asked Catherine the Great to send Cossacks to fight with the British. She refused.
France, Spain, and the Netherlands were the European allies of the nascent United States in the American Revolution. The Americans also had numerous Native American allies: Oneida, Tuscarora, Watauga Association, Catawba, Lenape, Chickasaw, Choctaw, Mahican, Mi'kmaq (until 1779), Abenaki, Cheraw, Seminole, Pee Dee, and Lumbee. Finally, the Indian (from India) Kingdom of Mysore also launched a war against the British contemporaneously with the American Revolution. This diversion of British soldiers to India helped the nascent United States from being overwhelmed with soldiers, making Mysore a de facto ally, even though there was minimal contact between Mysore and the nascent United States.
The American Revolution was against Britain. It's allies were Spain and France.
The allies helped fight against the British and get supplies. They also gave money. (French mostly) Allies were a big help in the revolution.
American Revolution
The American Indians
France and Spain
They were their allies. France furnished a Navy and 10,000 troops to the Continental Army.
In Europe - the Seven Years war, fought between British led allies and French led allies. In North America - the French and Indian war, which was fought between Great Britain, her North American colonies, native American allies and France, with its colonies and allies. The British won the war in North America, which ended with the Treaty of Paris (1763). This is considered the birth of Britain's Imperial Empire, as London was granted full control of North America, French India and most of the Caribbean.
Back then it was very rare for the bodies of the dead to be shipped back to their country of origin unless they were of high rank and distinction. Therefore, the remains of British soldiers and their allies can be found anywhere they engaged American forces during the war.
British, French, American. And not much French.