The paper aims to identify those factors that cause changes in the speed and strength of the international transmission of output shocks from the US to specified European economies. These factors are identified through the use of generalized impulse response functions conditioned on histories defined by an abrupt transition VAR. The chosen transition variables comprise changes in exchange rates, financial prices, international capital flows, trade links and monetary policy instruments. Besides the identification of asymmetric responses, the proposed model is useful in analyzing the strong effect of the recent US recession on the European economies and changes in business cycle synchronization over time.