The reason the dollar is staying strong is because markets have continued to price in more Fed tightening.
Oil prices have continued to move higher and equities have apparently taken it badly.
The dollar is continuing to respond to the new shift in tone from the FOMC yesterday, and that has continued to work through, not only on the currency market but also on the interest rate and equity markets.
The yen continued to strengthen this morning at the expense of high yielding currencies such as Australian and New Zealand dollars as well as the US dollar.