As an ideology, communism is generally regarded as hard-left, making fewer concessions to market capitalism and electoral democracy than do most forms of socialism. As a system of government, communism tends to center on a one-party state that bans most forms of political dissent. These two usages of the term "communism" – one referring to theory, the other to politics as they are practiced – need not overlap: China's ruling Communist Party has an explicitly pro-market capitalist orientation and pays only lip service to the Maoist ideology whose purist adherents (Peru's Shining Path in its heyday, for example) regard Chinese authorities as bourgeois counterrevolutionaries.
Socialism can refer to a vast swath of the political spectrum, in theory and in practice. Its intellectual history is more varied than that of communism: the Communist Manifesto devotes a chapter to criticizing the half-dozen forms of socialism already in existence at the time, and proponents have taken just about every left-of-center stance on the ideal (or best achievable) structure of economic and political systems.
bite me, moron
Over taxation and excessive spending are two of the current consequences of European socialism.
Socialism even in moderate 'pick and choose' forms requires a massive government infrastructure to control centers of national manufacturing, healthcare, education, and internal security forces. Not to mention spending to subsidize a large percentage of its population for guaranteed housing, food programs, etc. I don't know about you but surrendering means of manufacturing to the government seems like big risk.
And even if an American socialism was to follow the European model of state regulation of industry versus outright ownership, you're still throwing your economic fate solely in the hands of bureaucrats vulnerable to whim and fancy, only their greed now expands across all means of production.
The step to communism from socialism can be a very small one. Once government has become a monolithic owner of economic and industrial bases, citizens become very vulnerable to becoming market hostages of the State. Any form of mass resistance or take back of economical control by the people could result in suspension and then removal of individual rights and freedoms. Collectivism and group politics is a set of matches we Americans do not want to play with.