Of course, for the last two, you may do very well and enjoy a fulfilling career and never move on to a civil service position. Be sure to distinguish between the national, state, and local levels. The US government tends to pay more, have more interesting jobs and be more competitive. States and cities vary widely. On the other hand, a non-resident may be at a disadvantage and it is harder to use your contacts.
Counties pay about a third less than cities, which decreases the competition.
You can gain experience and move on later. Nonprofits offer many opportunities. Because they are often understaffed, you will have more responsibility and variety. Because they depend on grants they cannot offer secure employment, which decreases your competition. You can gain experience and move on later.