The first round of QE seems to have substantially reduced bond yields not only in the US, but also in Germany, Japan and the UK.6 It also contributed to the weakening of the US dollar, although the impact on net exports is a bit harder to assess.7 The evidence for ECB policy spillovers is, on the other hand, much weaker.
This may in part be due to the fact that the European Central Bank focused on reducing intra-Euro yields. These operations actually lifted German bond yields as the safe heaven effect subsided and in fact strengthened the Euro. The net sale of Eurozone bonds (i.e. net inflows) was strongly  2  See e.g.