The correct answer here is that they enacted policies that would benefit the merchants.
In mercantilism, the point was to take all the raw materials from the colonies for the mainland, for example the Great Britain. Those materials would be used to create goods which would then be sent and sold back to the colonies. That task fell to merchants who used the deals with the government to set their shop in the colonies and sell their goods. In return they paid for the army.
The United States, at the time in 1824, is closer to the Oregon Territory and acts as a national barrier. Arguably, Britain would have a difficult time reaching the Oregon Territory through The United States. Henceforth, I believe The United States has an advantage in making a claim.
