It's also worth noting that things like the common cold and European disease that we were imune to the native population weren't our (European) common illness's killed off about a half of the native populations before any sort of war started, therefore weaking the natives constiderably.
As for the war against the ENGLISH, well, the ENGLISH were have a little trouble else, and it's not like the actually had an army in America, i think toruble at home in Scotland and Ireland as well as European and the Caribean would have had there army well over streched
1746 - Battle of Culloden, The British Army made from Scottish and English soldiers, led by the Duke of Cumberland fight the last major battle on British mainland soil against French supported Scottish rebel Jacobites.
1755 - Seven Years' War begins.
1759 - British forces, led by General James Wolfe, takes French Quebec.
1775 - American War of Independence begins.
17 June - Battle of Bunker Hill
1777 - British defeat at the Battle of Saratoga.
1778 - British victory at the Battle of Long Island.
1793 - War on revolutionary France declared
1775–1783 American Revolutionary War or American War of Independence
1778–1783 Anglo-French War
1779–1783 Anglo–Spanish War
1780–1784 Fourth Anglo-Dutch War
Remember that if you're making an army, it's not always the best idea to have people in it that fucking hate you and your country (that's just a bad idea) as in the Scottish, if your fathers been killed by the English and then suddenly your in the English army and getting sent of to die for England you're not going to be to stoked
http://en.wikipedia.org/wiki/American_War_of_IndependenceThis sums up the British naval position which had helped them win every war, ohh they can't use the navy, ohh no proper troops, ohh the French are being dicks and they're only across the channel.
Also you can forget the French Americans were using gorilla tactic with the Natives to help you win there war - ohh how that back fired for them later on, once "America" began to expand and genicide of the local population was seen as an "ok" thing to do
If the English had wanted to keep the Americas i think they would have, instead they kicked the shit out of every country on Earth a bunch of times and let the Americas develope, while Britain dominated the rest of the world.
America didn't really become a super power until the end of the 1880 when they began to model there army on the British, well they began to model there Navy i should say and took example on how somewhere such as Britain had repelled and invaded pretty much anywhere they's really wanted simply using the Navy and better gun fire, don't forget an extra 2 inchs on a bayonet will make the enemy shit themselves