The British army, because of the prior 100 years of naval colonial dominance and a strong economy in general, ensured their soldiers were well equipped, disciplined, paid and fed. Those were not small feats for a military power at the time.

What particularly highlights the British army experience with relevance to the American Revolution, is the French and Indian War. The British fought hard to protect the colonies, at great economic cost and at great cost to English lives. 42,000 British soldiers fought up until 1763 to stake their investment in the continent.

The reason the British were so reluctant to give us our independence was in part because of the wars it fought to protect us. So your question actually is quite interesting because without the their hardened experience fighting wars in the Americas, they probably would've had an easier time allowing independence.

At the start of the war, the British army was coming off of a decade of peacetime service. In Fusiliers, Mark Urban makes the argument that the British garrison in Boston was actually in pretty poor shape - lazy officers, lax drill, limited practice at field maneuvers, that kind of thing - which helps explain their poor performance at Lexington, Concord, and especially Bunker Hill.

The strength of the British military is that it did have a core of professionals: officers that viewed themselves as career military and soldiers who signed up for lifetime commitments to the army. Once the army shifted to a wartime footing (Urban points to the large number of officers that resigned or were transferred after the evacuation of Boston), they were able to quickly adapt to fighting in America. The army that landed in New York in August of 1776 was a much more capable force than when it had left Boston in March of that year.