Is it legal to start a Litecoin mining pool in the US? My question is this: Given all the regulations in the USA, is it legal for me to start my own litecoin mining pool here in the US?
There is nothing illegal in the process of mining litecoins or bitcoins. 

As far as cryptocurrnecies concern, you should be worried about "money transmition" and "money laundering". If you do not hold other people's coins you are not breaking any laws.