The successful attempt of the 13 Colonies to free themselves from unfair British taxation did not come cheap. Both sides suffered many casualties, and great suffering was inflicted on the civilian population. Civilian casualties were, per se, kept at a minimum, but many civilians were rounded up and drafted into both armies, thereby getting in harm's way.
The economies on both sides of the Atlantic Ocean suffered tremendously, with Britain being at a distinct disadvantage by having to ship their troops and supplies over several thousand miles, during which time they could also be engaged in combat by enemy ships.
Also, relationships between France and the aspiring Free States flourished. France supplied much training in warfare as well as food supplies and war materiel.
England's national debt ballooned from 72,289,673 in 1775 to 129,586,789 in 1783, an amount that would be in the trillions of dollars in today's terms. The irony of this is that the amount of taxes that were collected from the Colonies amounted to a fraction of what was spent on warfare, but national pride and the commodities that were brought to England from the Colonies were the main reason the British wanted to maintain control. Tobacco, sugar and rice were easy to cultivate and transport from the New World, and the new trade routes to New Orleans and Central America brought new and desirable foods and lumber, as well.
With the Revolutionary War in progress, shipping was severely handicapped, as riding the Gulf Stream became too dangerous for the ships of the British Empire, adding weeks to the crossing times, with more ships lost to the rough seas they encountered on the alternate route.
As far as the human toll was concerned, approximately 50,000 men died on both sides of combat-related injuries, disease and in prisons. There were tens of thousands of injuries as well, most of them being severe, as the average musket ball fired from those 10-pound muskets weighed a whole ounce, causing severe injuries. Due to lack of proper care and with antibiotics still a few generations away, gas gangrene and infections led to many amputations.
Colonial slave owners faced a situation where their slaves were running away amidst the chaos to join the fight with the British forces, who gladly enlisted them into their ranks with the promise to become free men. Of the 1,500 who did so, only about 300 actually made it to England and freedom.
Many Native Americans joined the British as well, with Joseph Brant, a Mohawk chief who advocated alliance with Britain against American forces in the Revolutionary War in the lead.
The ultimate casualty
The greatest casualty was to England. They lost the colonies and cheap supplies coming from the American continent. But in the long run, they gained an invaluable ally, which helped them prevail in two world wars.