There are clearly other factors differentiating Somalia and the US. If there weren't, there would be massive starvation in Somalia because you can't get by on $145 a year in the US.

There's a couple of things going on there. One is that Somalia is in fact a very malnourished country. Another is that the GDP figures DanielLC cites are nominal, not based on purchasing power parity, and therefore can be skewed by exchange rates. The currencies of poor third-world nations tend to be very weak, so going by nominal GDP will end up making them look even poorer than they actually are.

PPP estimates for Somalia seem uncommon for some reason, but the CIA estimated a per-capita annual value of around $600 USD in 2010.