Final answer:
The UK ended their preferential tariffs with British North America due to the taxation of imports by Continental Europe and the United States and the British government's desire for free access to foreign markets.
Step-by-step explanation:
The British North America ended their preferential tariffs with the UK for a few reasons. One reason was that the governments of Continental Europe and the United States started taxing imports with tariffs to protect their own industries. This meant that British manufactured goods became more expensive in those markets, making it harder for British North America to compete. Additionally, the British government, which was dominated by free-traders, wanted to abolish customs duties and have free access to foreign markets, which meant ending preferential tariffs with British North America.