The industrial revolution did.
In the beginning, the only perceived difference was that they were not Christians so they wanted to baptize them. After the industrial revolution, the European countries developed rapidly while African and Asian countries didn't and Europeans believed that this was due to their superior race so they decided to colonize them under the pretense that they would help them develop.
Answer:
1. The style of fighting in America was much different than in Europe. Guerilla Warfare was popular among the American armies.
2. It is easier to supply your armies when you are fighting on your home turf. England had to load their supplies on ships while the colonists already had their supplies close to them.
Some other reasons:
The French.
British Arrogance.
Political Division in Great Britain.
It should be to pay off the national debt
There are 16 chapters in old yeller