American conservatism is many things but everything that makes up American conservatism is contained within the concept of free trade.
Free trade is built around a belief in property rights; that you have the right to own property and the right to control it. It is fundamental that the right own and control property is the right to improve your property and to benefit from it.
These are the very foundations of the social order on which the United States was built. The idea that you have the right to property and the right to benefit from its use and gather its fruits is fundamental to American conservatism.
Free trade is the acceptance of property rights and the right to dispose of property freely and without government interference. Its support by government is government support for the general welfare. Its obstruction by government, on the other hand, is the crony capitalist protection of special interests and monopoly.
The right to trade with our fellow man is a natural right that precedes the existence of government. Restrictions on trade by kings, princes or presidents undermine this God-given natural right.
When government promotes free trade it promotes individual liberty and the rights of man. Restrictions on trade are, by definition, corrosive of this fundamental natural right.
Trade that can only occur with permission of a sovereign is absolutely, positively hostile to the rights of man and American conservatism.