The economy of the smaller country (Canada) is much more dependent on the economy of the larger country (US) than vice versa. The US is significantly more powerful on the global political and economic stage than Canada. The same economic and political relationship will likely emerge with an independent Scotland. The northern country is heavily integrated with the globally significant southern country.In 2009 73% of Canada's exports went to the United States, and 63% of Canada's imports were from the United States.[34] Trade with Canada makes up 23% of the United States' exports and 17% of its imports.[35] By comparison, in 2005 this was more than U.S. trade with all countries in the European Union combined,[36] and well over twice U.S. trade with all the countries of Latin America combined.[37] Just the two-way trade that crosses the Ambassador Bridge between Michigan and Ontario equals all U.S. exports to Japan. Canada's importance to the United States is not just a border-state phenomenon: Canada is the leading export market for 35 of 50 U.S. states, and is the United States' largest foreign supplier of energy.
A more likely argument for independence is the different social agenda that the Scottish public appear to have. One example from post devolution Scotland is the provision of university education. English universities charge increasing fees to English students whereas Scottish students are educated for free in Scotland. There are many issues where Scotland wants to deviate from UK law and although it already has many powers to do so there are still powers that it does not have. Aside from a distinct social agenda and culture Scotland also has a distinct geography, population distribution and natural resources. I assume that nationalists have plans about how to provide legislation that is tailored to these differences rather than the whole of the UK. For some time I have considered the economic arguments for and against independence to be red herring. If there is an argument for independence it is more likely to be a very simple one about autonomy. I don't support independence or argue in favour of it but I can see why some people would like it.