IMHO the main reason the US is experiencing what we feel is a "slow" economy is relativity: We (and most of Europe) are used to an unusually robust economy that had little or no competition from China, Russia, India, Brazil, Vietnam, etc., etc.
Now we are beginning to feel the effects of very strong global competitive changes, and these will only get stronger.
No, that's another myth. This one is commonly believed on the left as well as the right.
Let's consider a developing country with a cheap labor force, and a U.S. manufacturer making a complicated product such as a modern car, using a highly-paid, expensive labor force. The car maker does several things.
1) He automates his American factories, reducing his need for labor, and lays people off. The jobs remaining are complex, high-tech kinds of jobs that are still paid very well.
2) He makes use of the cheap foreign labor to produce some of the simpler parts, laying off more expensive American workers and closing down American parts factories.
What happens to the workers he lays off? Do they remain unemployed long? As it turned out, no, they didn't; they got other jobs, mostly in the service sector. Those jobs didn't pay as well as the manufacturing jobs that were lost.
But why didn't they? Because they were not unionized, where manufacturing for the most part was. And it proved extremely difficult to form unions in them, because before all this happened the government had changed its approach to enforcement of labor rights. Illegal firings and other illegal means of suppressing union formation have soared; when a company gets caught, it just shrugs and pays the fine, which it regards as an acceptable cost of doing business.
Suppose that had not been true, and the government had retained its same pro-labor stance it had in the '50s and '60s? Suppose, in result, that the service sector was now unionized? Would we be in danger of losing those jobs to foreign companies, too?
No, not really, because most of those jobs are ones that MUST be filled by Americans. There are some very low-level customer service jobs that have been outsourced to India and Pakistan, where many English speakers are available, but even that has not been an unqualified success.
David Ricardo was right, and remains right: comparative advantage still rules. The problem we have, and the reason for the decline in real wages, is internal and political, not a matter of foreign competition.