President Trump's announcement of tariffs on imports from countries worldwide has rocked the stock market -- and the tech-heavy Nasdaq Composite (^IXIC 12.16%) has led the decline, crashing more than 20% from its most recent high.Why are tech stocks being hit so hard? These companies rely on production of parts and finished goods in countries around the world, from China to India -- and the companies now will have to pay the new import duties as they bring these items into the U.S.All this has prompted inve ...