It is only the US that has the capacity to autonomously lower its interest rates to whatever it considers appropriate for stimulating aggregate demand (which would then allow other countries too to lower their interest rates). But the interest rates in the US for much of the recent period were close to zero and still there was no revival of the world economy. On the contrary, such low interest rates maintained over a long period had the effect of emboldening corporates in that country to raise their profit mark-ups and give rise to an acceleration of inflation, as has occurred of late.