What changes were in France, England, Italy, Germany in the period 1800-1870?

By 1870, Germany and Italy were able to fully unite into one state. Hundreds of years before that, dozens of cities and small states existed on their territory. Thanks to this, unified state entities began to better defend national policies around the world.
France experienced a period of rise under Napoleon, but then gradually began to lose strength in Europe and influence, building its colonial empire in Africa and Asia.
Great Britain continued to reign on the seas, gradually losing its position in Europe, but trying to pursue its policy everywhere and everywhere, which is why it regularly changed its allies for the sake of momentary goals of maintaining dominance over the world.