Is it a sign of weakness is a national economy manufactures few of the goods that it consumes?

An economy cannot be totally reliant on services alone. However a service-economy is a sign of economic growth and development of the country. It's not a sign of weakness, rather it shows the strength of the economy.

A service-based economy will be reliant on other countries for manufacturing products and catering to the demand of primary and secondary markets. However, no market is a pure service oriented market and US is no exception. So it's not a sign of weakness nor is it bad that US is a service-based economy. It just means that they have a highly skilled and competent workforce who work in the tertairy sector. But don't forget that US also has primary and secondary sectors- but they're not that dominant as compared to tertiary sector.