Growth hopes to boost Global Equities

As the US markets were closed today, markets opened around the world with gains. With good news still overflowing from last week especially about employment. Stocks around the world showed gains today. Even though the IMF warned of weak growth.

What state is the US Market in? Do the US markets depend on other markets?

Theres a quote in the article that says "Merger and Acquisition activity was the most active since 1999"

What does this mean for US markets, is our markets actually shrinking if companies are buy their competition or other businesses?