All three civilizations preferred trade to isolation; although isolation did provide some protection from invasion. The cataracts on the Nile River and surrounding desert provided considerable protection for Egypt, and the Indus Valley was largely protected by the Hindu Kush. Mesopotamia, not so protected, saw the rise and fall of a number of empires.
In Egypt, the Nile itself lent itself to trade; in fact the city of Aswan derives its name from an Ancient Egyptian word meaning "trade." Lenin cloth from Egypt was traded for Ivory and also cedar from Lebanon for construction.
There is evidence of Mesopotamian influence in ancient India, particularly the existence of a deity represented by a bull, most likely borrowed from the Babylonian god Baal. The Dravidians traded pottery, ivory and pearls for wood, leather, and even olive oil. They also traded with Persia for gold and precious gems.
The Phoenicians of Mesopotamia were the foremost traders of the age; in fact their entire empire was based on trade. They were accomplished sailors and lent a great deal of their culture to other areas through trade, including their "phonetic" Alphabet.
More extensive ancient trade is described in the link below.