WHY USD IS ACCEPTED GLOBALLY

WHY USD $ IS USED WORLDWIDE FOR ALL THE TRADE AND ALSO AS RESERVE?

Around $580 billion in U.S. bills are used outside the country.More than one-third of the world's gross domestic product comes from countries that peg their currencies to the dollar. That includes seven countries that have adopted the dollar.More than 85 percent of forex trading involves the U.S. dollar. Furthermore, 39 percent of the world's debt is issued in dollars.
China and India alone holds foreign reserves of $2 trillion

WHY EVERYTHING IS DOLLAR AND MOST COUNTRIES ARE USING THE $USD AS A RESERVE ALONG WITH GOLD? 

So,lets go back to the history what made USD more powerful.

BRETTON WOOD AGREEMENT:

The 1944 Bretton Woods agreement kickstarted the dollar into its current position. Before then, most countries were on the gold standard. Their governments promised to redeem their currencies for their value in gold upon demand. The world's developed countries met at Bretton Woods, New Hampshire, to peg the exchange rate for all currencies to the U.S. dollar. At that time, the United States held the largest gold reserves of 65% . This agreement allowed other countries to back their currencies with dollars, rather than gold.

By the early 1970s, countries began demanding gold for the dollars they held. They needed to combat inflation. Rather than allow Fort Knox to be depleted of all its reserves, President Nixon separated the dollar from gold. By that time, the dollar had already become the world's dominant reserve currency.