During the American Revolution, why couldn't the Royal Red Guards defeat the American militia (without the help of France)?

There are many factors contributing to the victory of the American War of Independence, among which I think there are racial and religious factors.

First, Britain was the world hegemon at that time, colonizing the whole world. However, most of the people he colonized and plundered were non-Caucasians, such as China, India (although white, after all, there was a big racial gap), Africa and Southeast Asian countries. America was originally a new colony formed by a large number of European and British immigrants. The same race, the same language and the same religion made Britain have little international support during the War of Independence. Similarly, the army has also considered whether it is correct to suppress colonial compatriots.

Second, the technological development at that time made the British navy still in the era of navigation. If we want to win the American war, we need to transport a lot of people, materials and equipment to the United States. At that time, the carrying capacity at sea was limited, and the ability to invest troops at one time was insufficient, which made the war a "refueling war", and it was difficult to quickly eliminate the main force of the American Continental Army and become a military taboo. It was not until the Opium War that the world navy developed to age of steam that it had the strength to attack other countries from a long distance.

Third, Britain made many enemies in Europe at that time, and France, Spain, the Netherlands and other countries were eyeing it. Weighing the pros and cons, it is impossible to focus the attention of a large number of countries on distant America, and Europe is still unstable. It was not until the Battle of Trafalgar in 1805 that Britain really consolidated its maritime hegemony and began a confident expedition. So China began to enter the semi-colonial era.