Final answer:
The British likely attacked from the sea because they knew the Americans had a small navy and could not defend all their seaports, giving the British naval superiority and a strategic advantage.
Step-by-step explanation:
The statement that probably explains why the British first attacked from the sea is that they knew the Americans did not have any ships. The information provided indicates that the American defenses were stretched thin, especially along the Atlantic coast due to the U.S.'s small navy. Consequently, the British recognized that Americans could not adequately defend all their seaports at the same time. During the height of the Napoleonic Wars, Britain had not allocated its full military force against the United States, but after the end of these wars, the British sought to avenge American actions in Canada. Knowing the weaknesses of American naval defenses, attacking from the sea gave the British a strategic advantage.
Moreover, the British first attacked from the sea because their navy was superior. Given that Americans had made attempts to invade Canada and had a small navy, the British were likely to choose an attack vector that played to their strengths and exploited the vulnerabilities of the American defenses. Thus, an attack from the sea was a logical choice for the British.