How was Britain able to resist Hitler and the Nazis?

After the evacuation from Dunkirk, Britain waited for the Germans to cross the English Channel, and invade Britain while we were still in disarray. Thankfully, Hitler hesitated on the very coast of France and postponed the invasion, giving Britain time to reassemble their forces. What followed was the Battle of Britain, when the RAF tried to keep supremacy of the sky, then the blitzing of London and major cities. Eventually, after America's Pearl Harbour, the USA declared war on Japan, and Hitler declared war on the USA. This meant that the President of America, Franklin Delano Roosevelt, was able to come directly to Britain's aid.