I was in a very similar situation and I spent my army service time to study TOEFL and SATs.
I generally recommend going through a US college. The process is much tougher because of general education requirements (involving writing and US history & literature). However, this process will make you read and write better English. You will become slightly more culturally compatible (Depending on how hard you try to get immersed into US friends, even if they repel you.)
Your ability to read and write will affect your academics throughout your undergraduate and professional side of your US life.
Your ability to speak freely will affect your social well being and happiness. However, at your age, this may not matter much.
If you could spend 36 months of your employment in improving these basic skills set, I would go for it.
Completing your army service as soon as possible appears to be a priority.
For your speaking ability, earlier the better. But you are relatively late anyway (like myself).