Have you heard of the word "conscription"?

The last time United States have constription is during Vietnam War. Of course the last large-scale conion is WWII.
公民真的會被美國不經自己同意強製服兵役征兵.

Regarding his concern, it is not ungrounded. Actually, one of my friends (an american mother) told me she is worried about current war progress since she is afraid conion might be needed, and she has two boys (although they are only around 10 right now...)