Leaffan has already given the answer: most European countries are parliamentary democracies, with stronger party discipline than in the United States. If the party in power is convinced that it needs to do something that is politically unpopular but in the long term national interest, it is much easier for them to do so than in the United States congressional system.
For instance, in Canada, the Progressive Conservative government of Brian Mulroney brought in the Goods and Services Tax, a sales tax, which was massively unpopular. The PCs traditionally ran on a low tax platform, but they were convinced by the economic arguments that the previous system, which included a hidden 13% manufacturing tax, made Canadian industries less competitive internationally. They abolished the manufacturing tax and brought in the GST at 7%.
They did pay for it at the next election, but by that time the PCs were so unpopular that it’s hard to point to that alone as the reason for their defeat. However, the incoming Liberals, who had campaigned on abolishing the GST, crunched the same economic numbers and found that the economic argument in favour of the GST was compelling. They decided not to abolish it, and we still have it, 20+ years later. The Liberals took flak for that about-face, and is still one of the criticisms made about Prime Minister Chrétien, but it wasn’t a career-killer for anyone.
Similarly, in the 90s, Canada faced substantial deficits at both the federal and provincial levels. All governments realised the magnitude of the problems they faced, and instituted major cost-cutting programs to get rid of their deficits. By and large, they succeeded, giving Canada a lot of extra spending power when we needed it in the recent recession. The federal government is currently in a deficit situation, but all of the parties campaigned on plans to bring the government back into a positive budget balance within the next four years or so. Given the past track record, there’s no reason not to think the feds won’t manage to do so, even if it means cost-cutting.
Overall, both these examples illustrate, in my opinion, that one of the strengths of the parliamentary system is that it allows governments with firm majorities to bring in unpopular policies and see how they work, rather than just kicking the can down the road.