Why did Europeans prohibit trading between the different American colonies founded by different countriea

Back then Europeans prohibit trading between the different American colonies because the practice Mercantilism, which means that they wanted to keep all their wealth to themselves.

When Trades between two entity happens, both wealth of the trading partners will increase due to the profit that they generate through the trades. The Europeans do not want this to happen because they wanted to keep America powerless and under their control.