Really some posts before I saw US got the combat engineers armed with Grease gun, my impression is that US will be like the old Brit, u have to tech to T1 or T2 to get Engineer (sapper) to lay mines. No way Relic can create a faction with no access to AI mines.
Or you can listen to the alpha tester who has been playing with them for the past 3 weeks when I say: No, they do not have access to an non-doctrinal AI mine.
All factions have disatvantages. Considering all the great things you've learned about the Americans so far is it really that odd to learn they lack something.